[Bugfix] Fix dynamic FP8 quantization for Mixtral (#4793)

vllm/model_executor/models/mixtral.py

@@ -95,7 +95,7 @@ class MixtralMoE(nn.Module):
                                      params_dtype=self.params_dtype,
                                      quant_config=None)
 
-        if self.use_fp8:
+        if self.use_fp8 and self.quant_config.is_checkpoint_fp8_serialized:
             params_dtype = torch.float8_e4m3fn
 
         self.w13_weight = nn.Parameter(