[Hybrid][torch.compile] Refactor mamba2 forward to avoid obscuring linear projections under custom op (#28587)

Signed-off-by: Tomer Asida <57313761+tomeras91@users.noreply.github.com>

vllm/model_executor/models/zamba2.py

@@ -567,11 +567,7 @@ class Zamba2MambaDecoderLayer(nn.Module):
         hidden_states = self.input_layernorm(hidden_states)
 
         # Process through Mamba mixer
-        output = torch.empty_like(hidden_states)
-        self.mamba(
-            hidden_states,
-            output,
-        )
+        output = self.mamba(hidden_states)
 
         # residual connection after mamba
         hidden_states = residual + output