[Ops] Fix bug in register_custom_ops without forward_context (#2883)

### What this PR does / why we need it?
This PR fixed the bug in register_custom_ops without forward_context. We
set try-except to consider this situation.

### Does this PR introduce _any_ user-facing change?
No.

### How was this patch tested?
CI passed with new added/existing test.

- vLLM version: main
- vLLM main:
7920de0a2a

Signed-off-by: rjg-lyh <1318825571@qq.com>

vllm_ascend/envs.py

@@ -139,11 +139,13 @@ env_variables: Dict[str, Callable[[], Any]] = {
     "VLLM_ASCEND_ENABLE_PREFETCH_MLP":
     lambda: bool(int(os.getenv("VLLM_ASCEND_ENABLE_PREFETCH_MLP", '0'))),
     # buffer size for gate up prefetch
-    "MLP_GATE_UP_PREFETCH_SIZE":
-    lambda: int(os.getenv("MLP_GATE_UP_PREFETCH_SIZE", 18 * 1024 * 1024)),
+    "VLLM_ASCEND_MLP_GATE_UP_PREFETCH_SIZE":
+    lambda: int(
+        os.getenv("VLLM_ASCEND_MLP_GATE_UP_PREFETCH_SIZE", 18 * 1024 * 1024)),
     # buffer size for down proj prefetch
-    "MLP_DOWN_PREFETCH_SIZE":
-    lambda: int(os.getenv("MLP_DOWN_PREFETCH_SIZE", 18 * 1024 * 1024)),
+    "VLLM_ASCEND_MLP_DOWN_PREFETCH_SIZE":
+    lambda: int(
+        os.getenv("VLLM_ASCEND_MLP_DOWN_PREFETCH_SIZE", 18 * 1024 * 1024)),
     # Whether to enable dense model and general optimizations for better performance.
     # Since we modified the base parent class `linear`, this optimization is also applicable to other model types.
     # However, there might be hidden issues, and it is currently recommended to prioritize its use with dense models.