[Moe Refactor] Make Inplace Flag for FusedMoEModularKernel part of the constructor (#33375)

Signed-off-by: Bill Nell <bnell@redhat.com>
Co-authored-by: Robert Shaw <114415538+robertgshaw2-redhat@users.noreply.github.com>

vllm/model_executor/layers/quantization/mxfp4.py

@@ -881,10 +881,6 @@ class Mxfp4MoEMethod(FusedMoEMethodBase):
                     f"Incompatible Mxfp4 backend ({self.mxfp4_backend}) for EP"
                 )
 
-    @property
-    def allow_inplace(self) -> bool:
-        return True
-
     @property
     def is_monolithic(self) -> bool:
         return (
@@ -923,6 +919,7 @@ class Mxfp4MoEMethod(FusedMoEMethodBase):
                 activation=layer.activation,
                 expert_map=layer.expert_map,
                 input_dtype=self.marlin_input_dtype,
+                inplace=not self.moe.disable_inplace,
             )
 
         assert _can_support_mxfp4(