Fix the device error when using ray as vllm-acend backend (#884)

1. Remove RAY_EXPERIMENTAL_NOSET_ASCEND_RT_VISIBLE_DEVICES
2. Add lazy init for vllm_ascend_C

Signed-off-by: zhuo97 <1103045176@qq.com>

tests/e2e/singlecard/ops/test_rotary_embedding.py

@@ -10,7 +10,9 @@ import pytest
 import torch
 import torch.nn as nn
 
-import vllm_ascend.platform  # noqa: F401
+from vllm_ascend.utils import enable_custom_op
+
+enable_custom_op()
 
 # Only Neox style true scenario is supported for now
 IS_NEOX_STYLE = [True]