[Model] Add has_weight to RMSNorm and re-enable weights loading tracker for Mamba (#10739)

Signed-off-by: Isotr0py <2037008807@qq.com>

vllm/model_executor/layers/layernorm.py

@@ -20,6 +20,7 @@ class RMSNorm(CustomOp):
         hidden_size: int,
         eps: float = 1e-6,
         var_hidden_size: Optional[int] = None,
+        has_weight: bool = True,
     ) -> None:
         super().__init__()
 
@@ -27,7 +28,11 @@ class RMSNorm(CustomOp):
         self.variance_epsilon = eps
         self.variance_size_override = (None if var_hidden_size == hidden_size
                                        else var_hidden_size)
-        self.weight = nn.Parameter(torch.ones(hidden_size))
+        self.has_weight = has_weight
+
+        self.weight = torch.ones(hidden_size)
+        if self.has_weight:
+            self.weight = nn.Parameter(self.weight)
 
     def forward_native(
         self,
@@ -59,7 +64,9 @@ class RMSNorm(CustomOp):
         variance = x_var.pow(2).mean(dim=-1, keepdim=True)
 
         x = x * torch.rsqrt(variance + self.variance_epsilon)
-        x = x.to(orig_dtype) * self.weight
+        x = x.to(orig_dtype)
+        if self.has_weight:
+            x = x * self.weight
         if residual is None:
             return x
         else: