testsuite/arm: Add arm_hard_ok check in armv8_2-fp16-scalar-2.c

This test relies on -mfloat-abi=hard to pass (otherwise
test_mov_imm_[12] directly build the 1.0 fp16 representation via movw
r0, #15360 rather than using vmov.f16 s0, #1.0e+0 as expected by
scan-assembler-times)

Adding the arm_hard_ok check makes the test unsupported eg. on
arm-linux-gnueabi instead of reporting a failure.

2021-03-20  Christophe Lyon  <[email protected]>

	gcc/testsuite/
	* gcc.target/arm/armv8_2-fp16-scalar-2.c: Add arm_hard_ok.

Author: Christophe Lyon

gcc/testsuite/gcc.target/arm/armv8_2-fp16-scalar-2.c

@@ -1,7 +1,9 @@
 /* { dg-do compile }  */
+/* { dg-require-effective-target arm_hard_ok }  */
 /* { dg-require-effective-target arm_v8_2a_fp16_scalar_ok }  */
 /* { dg-options "-O2 -std=c11" }  */
 /* { dg-add-options arm_v8_2a_fp16_scalar }  */
+/* { dg-additional-options "-mfloat-abi=hard" } */
 
 /* Test compiler use of FP16 instructions.  */
 #include <arm_fp16.h>