[MISC] Clean up torch_npu (#688)

torch_npu 2.5.1 support autoload now. This patch does:
1. remove useless torch_npu import
2. replace `torch_npu.npu` to `torch.npu`.

Signed-off-by: wangxiyuan <wangxiyuan1007@gmail.com>

vllm_ascend/distributed/device_communicators/pyhccl.py

@@ -19,7 +19,6 @@ from typing import Optional, Union
 
 import torch
 import torch.distributed as dist
-import torch_npu  # noqa: F401
 from torch.distributed import ProcessGroup, ReduceOp
 from vllm.distributed.utils import StatelessProcessGroup
 from vllm.logger import logger