[Refact]Refact MLA/SFA weight prefetch to consist with moe weight prefetch (#6629)

### What this PR does / why we need it?
1. [Refact] Refact MLA/SFA weight prefetch to consist with moe weight
prefetch
2. Remove duplicated o_proj weight prefetch in forward for MLA/SFA

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

### How was this patch tested?

1) Performance result:
Perf test data:
*) MLA:

| | 1st test | 2nd test | Output Token Throughput(Avg) | Performance
improvement percentage |
| --- | --- | --- | --- | --- |
| o_proj duplicate prefetch | 11.9669 token/s | 12.0287 token/s |
11.9978 |
| o_proj no duplicate prefetch | 12.5594 token/s | 12.6216 token/s |
12.5905 | 4.94%| |

single layer performace improve: 5%~8%

*) SFA:

| | 1st test | 2nd test | Output Token Throughput(Avg) | Performance
improvement percentage |
| --- | --- | --- | --- | --- |
| o_proj duplicate prefetch | 13.0523 token/s | 13.1084 token/s |
13.08035 | |
| o_proj no duplicate prefetch | 13.9844 token/s | 14.1678 token/s |
14.0761 | 7.6% |

- vLLM version: v0.15.0
- vLLM main:
d7e17aaacd

---------

Signed-off-by: leo-pony <nengjunma@outlook.com>

vllm_ascend/ops/fused_moe/moe_mlp.py

@@ -100,8 +100,7 @@ def quant_apply_mlp(
     _output_dtype = w2_scale[0].dtype
 
     weight_prefetch_method = get_weight_prefetch_method()
-    if weight_prefetch_method:
-        weight_prefetch_method.maybe_prefetch_moe_weight_postprocess(hidden_states)
+    weight_prefetch_method.maybe_prefetch_moe_weight_postprocess(hidden_states)
     is_mc2 = get_forward_context().moe_comm_type == MoECommType.MC2
     if w1_scale_bias is None and w1_offset is None and is_mc2:
         if _custom_gmm_swiglu_enabled(fusion, dynamic_eplb):