[Bugfix] rename enable_flash_comm_v1 back to enable_sp (#6883)

### What this PR does / why we need it?

PR #5632 introduced a bug by replacing some branches gated by enable_sp
with enable_flash_comm_v1. As a result, when enable_shared_expert_dp is
enabled alone (i.e., VLLM_ASCEND_ENABLE_FLASHCOMM1=0 and
VLLM_ASCEND_ENABLE_FLASHCOMM=0), the behavior becomes inconsistent with
the previous logic and leads to accuracy issues. This PR restores the
original enable_sp-based branching to recover expected behavior and
accuracy.

### Does this PR introduce _any_ user-facing change?

No

### How was this patch tested?

#### 1. start server
``` bash
vllm serve /home/weights/DeepSeek-V2-Lite-W8A8/  \
    --port 8001 \
    --served-model-name auto \
    --max-model-len 1024 \
    --enforce-eager \
    --tensor-parallel-size 2 \
    --data-parallel-size 2 \
    --gpu-memory-utilization 0.9 \
    --enable-expert-parallel \
    --additional-config '{"enable_shared_expert_dp": true}'
```

#### 2. curl
```bash
curl -s http://localhost:8001/v1/chat/completions \
-H "Content-Type: application/json" \
-d '{
  "model": "auto",
  "messages": [
    {"role": "user", "content": "Hello. I have a question. Who are you?"}
  ],
  "max_tokens": 10,
  "temperature": 0.0,
  "ignore_eos_token": true
}'
```

- vLLM version: v0.16.0
- vLLM main:
15d76f74e2

Signed-off-by: realliujiaxu <realliujiaxu@163.com>

vllm_ascend/ascend_forward_context.py

@@ -12,7 +12,7 @@ import vllm_ascend.envs as envs_ascend
 from vllm_ascend.ascend_config import get_ascend_config
 from vllm_ascend.utils import (
     AscendDeviceType,
-    enable_flash_comm_v1,
+    enable_sp,
     flashcomm2_enable,
     get_ascend_device_type,
     has_layer_idx,
@@ -92,14 +92,14 @@ def set_ascend_forward_context(
         # main model and drafter model may have different architecture
         is_context_moe_model = is_drafter_moe_model(vllm_config) if is_draft_model else is_moe_model(vllm_config)
         if is_context_moe_model:
-            flash_comm_v1_enabled = enable_flash_comm_v1() and num_tokens is not None
+            flash_comm_v1_enabled = enable_sp(vllm_config) and num_tokens is not None
             mmrs_fusion = False
         elif is_draft_model:
             # TODO: for dense drafter, `sp` is redundant and is not compatible with `dp` and `graph`.
             # Disable it to avoid more problems.
             flash_comm_v1_enabled = False
         else:
-            flash_comm_v1_enabled = enable_flash_comm_v1() and num_tokens is not None and num_tokens > 1000
+            flash_comm_v1_enabled = enable_sp(vllm_config) and num_tokens is not None and num_tokens > 1000
         forward_context.mmrs_fusion = mmrs_fusion
         forward_context.num_tokens = num_tokens
         forward_context.flash_comm_v1_enabled = flash_comm_v1_enabled