Fix issue of mismatched device

Signed-off-by: Jael Gu <mengjia.gu@zilliz.com>

mpvit.py

@@ -40,6 +40,9 @@ class MPViT(NNOperator):
                  skip_preprocess: bool = False):
         super().__init__()
 
+        if device is None:
+            device = 'cuda' if torch.cuda.is_available() else 'cpu'
+
         self.model = mpvit.create_model(model_name=model_name,
                                         num_classes=num_classes,
                                         pretrained=True,