[onnx] Fix create ONNX DFT op for scalar signal size (#32637)

### Details:
- The ONNX specification for DFT-17, DFT-20 operator defines
`dft_length` as scalar input which is not compatible with OV FFT
operators (Must be 1-D). In case of scalar input unsqueeze this input to
1-D.


### Tickets:
 - N/A

---------

Signed-off-by: Raasz, Pawel <[email protected]>

Author: praasz

src/frontends/onnx/frontend/src/utils/dft.cpp

@@ -12,6 +12,7 @@
 #include "openvino/op/idft.hpp"
 #include "openvino/op/irdft.hpp"
 #include "openvino/op/rdft.hpp"
+#include "openvino/op/reshape.hpp"
 #include "openvino/op/shape_of.hpp"
 #include "openvino/op/unsqueeze.hpp"
 
@@ -55,27 +56,31 @@ ov::Output<ov::Node> make_dft(const ov::Output<ov::Node>& signal,
         conversion_to_complex_applied = try_convert_real_to_complex(processed_signal);
     }
 
-    bool dft_length_provided = !ov::op::util::is_null(length);
+    const bool dft_length_provided = !ov::op::util::is_null(length);
+    const auto& signal_size =
+        dft_length_provided
+            ? std::make_shared<v1::Reshape>(length, v0::Constant::create(ov::element::i32, {1}, {1}), false)->output(0)
+            : length;
 
     ov::Output<ov::Node> result;
     if (is_inversed) {
         if (is_onesided) {
-            result = dft_length_provided ? std::make_shared<v9::IRDFT>(processed_signal, axis_const, length)
+            result = dft_length_provided ? std::make_shared<v9::IRDFT>(processed_signal, axis_const, signal_size)
                                          : std::make_shared<v9::IRDFT>(processed_signal, axis_const);
             if (conversion_to_complex_applied) {  // align the output shape with a real numbers representation
-                const auto unsqueeze_axis = v0::Constant::create(ov::element::i64, {}, {-1});
+                const auto unsqueeze_axis = v0::Constant::create(ov::element::i32, {}, {-1});
                 result = std::make_shared<v0::Unsqueeze>(result, unsqueeze_axis);
             }
         } else {
-            result = dft_length_provided ? std::make_shared<v7::IDFT>(processed_signal, axis_const, length)
+            result = dft_length_provided ? std::make_shared<v7::IDFT>(processed_signal, axis_const, signal_size)
                                          : std::make_shared<v7::IDFT>(processed_signal, axis_const);
         }
     } else {
         if (is_onesided) {
-            result = dft_length_provided ? std::make_shared<v9::RDFT>(processed_signal, axis_const, length)
+            result = dft_length_provided ? std::make_shared<v9::RDFT>(processed_signal, axis_const, signal_size)
                                          : std::make_shared<v9::RDFT>(processed_signal, axis_const);
         } else {
-            result = dft_length_provided ? std::make_shared<v7::DFT>(processed_signal, axis_const, length)
+            result = dft_length_provided ? std::make_shared<v7::DFT>(processed_signal, axis_const, signal_size)
                                          : std::make_shared<v7::DFT>(processed_signal, axis_const);
         }
     }

src/frontends/onnx/tests/models/dft_scalar_length_provided.prototxt

@@ -0,0 +1,71 @@
+ir_version: 7
+graph {
+  node {
+    output: "dft_length"
+    op_type: "Constant"
+    attribute {
+      name: "value"
+      t {
+        dims: 0
+        data_type: 7
+        int64_data: 1
+        name: "const_tensor"
+      }
+      type: TENSOR
+    }
+  }
+  node {
+    input: "data"
+    input: "dft_length"
+    output: "out"
+    op_type: "DFT"
+    attribute {
+      name: "inverse"
+      i: 0
+      type: INT
+    }
+    attribute {
+      name: "onesided"
+      i: 0
+      type: INT
+    }
+    attribute {
+      name: "axis"
+      i: 0
+      type: INT
+    }
+  }
+  input {
+    name: "data"
+    type {
+      tensor_type {
+        elem_type: 1
+        shape {
+          dim {
+            dim_value: 3
+          }
+          dim {
+            dim_value: 5
+          }
+          dim {
+            dim_value: 2
+          }
+        }
+      }
+    }
+  }
+  output {
+    name: "out"
+    type {
+      tensor_type {
+        elem_type: 1
+        shape {
+        }
+      }
+    }
+  }
+}
+opset_import {
+  domain: ""
+  version: 13
+}

src/frontends/onnx/tests/onnx_import_signal.in.cpp

@@ -124,6 +124,19 @@ OPENVINO_TEST(${BACKEND_NAME}, onnx_model_dft_length_provided) {
         {0.000000f, 0.000000f, 1.000000f, 0.000000f, 2.000000f, 0.000000f, 3.000000f, 0.000000f, 4.000000f, 0.000000f});
 }
 
+OPENVINO_TEST(${BACKEND_NAME}, onnx_model_dft_scalar_length_provided) {
+    auto model = convert_model("dft_scalar_length_provided.onnx");
+    auto test_case = ov::test::TestCase(model, s_device);
+    test_case.add_input<float>(Shape{3, 5, 2}, {0.000000f,  0.000000f, 1.000000f,  0.000000f, 2.000000f,  0.000000f,
+                                                3.000000f,  0.000000f, 4.000000f,  0.000000f, 5.000000f,  0.000000f,
+                                                6.000000f,  0.000000f, 7.000000f,  0.000000f, 8.000000f,  0.000000f,
+                                                9.000000f,  0.000000f, 10.000000f, 0.000000f, 11.000000f, 0.000000f,
+                                                12.000000f, 0.000000f, 13.000000f, 0.000000f, 14.000000f, 0.000000f});
+    test_case.add_expected_output<float>(
+        Shape{1, 5, 2},
+        {0.000000f, 0.000000f, 1.000000f, 0.000000f, 2.000000f, 0.000000f, 3.000000f, 0.000000f, 4.000000f, 0.000000f});
+}
+
 OPENVINO_TEST(${BACKEND_NAME}, onnx_model_dft_length_provided_onesided) {
     auto model = convert_model("dft_lenght_provided_onesided.onnx");
     auto test_case = ov::test::TestCase(model, s_device);