ops: Put weight cast on the offload stream (Comfy-Org#10697)

This needs to be on the offload stream. This reproduced a black screen
with low resolution images on a slow bus when using FP8.

Author: rattus128

comfy/ops.py

@@ -110,9 +110,9 @@ def cast_bias_weight(s, input=None, dtype=None, device=None, bias_dtype=None, of
                 for f in s.bias_function:
                     bias = f(bias)
 
-    weight = weight.to(dtype=dtype)
-    if weight_has_function:
+    if weight_has_function or weight.dtype != dtype:
         with wf_context:
+            weight = weight.to(dtype=dtype)
             for f in s.weight_function:
                 weight = f(weight)