[Bugfix] Fix FusedMoEModularKernel for triton backend (#28913)

Signed-off-by: Xin Yang <xyangx@amazon.com>

vllm/model_executor/layers/quantization/mxfp4.py

@@ -755,8 +755,10 @@ class Mxfp4MoEMethod(FusedMoEMethodBase):
 
             self.w13_weight = w13_weight
             self.w2_weight = w2_weight
-            layer.w13_weight = Parameter(w13_weight.storage.data, requires_grad=False)
-            layer.w2_weight = Parameter(w2_weight.storage.data, requires_grad=False)
+            del layer.w13_weight
+            del layer.w2_weight
+            layer.w13_weight = w13_weight
+            layer.w2_weight = w2_weight
         else:
             raise ValueError(f"Unsupported backend: {self.mxfp4_backend}")
 
@@ -1065,8 +1067,8 @@ class Mxfp4MoEMethod(FusedMoEMethodBase):
 
             return triton_kernel_moe_forward(
                 hidden_states=x,
-                w1=self.w13_weight,
-                w2=self.w2_weight,
+                w1=layer.w13_weight,
+                w2=layer.w2_weight,
                 gating_output=router_logits,
                 topk=top_k,
                 renormalize=renormalize,