!7346 GPU model zoo lenet remove amp

Merge pull request !7346 from VectorSL/gpu-lenet

model_zoo/official/cv/lenet/train.py

@@ -61,7 +61,7 @@ if __name__ == "__main__":
                                  keep_checkpoint_max=cfg.keep_checkpoint_max)
     ckpoint_cb = ModelCheckpoint(prefix="checkpoint_lenet", directory=args.ckpt_path, config=config_ck)
 
-    if args.device_target == "CPU":
+    if args.device_target != "Ascend":
         model = Model(network, net_loss, net_opt, metrics={"Accuracy": Accuracy()})
     else:
         model = Model(network, net_loss, net_opt, metrics={"Accuracy": Accuracy()}, amp_level="O2")