[Feat] Adapted mtp function to Qwen3-next (#3918)

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

Adapts mtp function to Qwen3-next.

- vLLM version: v0.11.0
- vLLM main:
83f478bb19

Signed-off-by: drslark <slarksblood@qq.com>

vllm_ascend/models/qwen3_next.py

@@ -260,6 +260,24 @@ class CustomQwen3NextGatedDeltaNet(Qwen3NextGatedDeltaNet, MambaBase):
             mixed_qkv_spec = None
             mixed_qkv_non_spec = mixed_qkv
 
+        # 2.1: process the mutli-query part
+        if spec_sequence_masks is not None:
+            mixed_qkv_spec = mixed_qkv_spec.view(
+                attn_metadata.num_spec_decodes, -1, mixed_qkv_spec.size(-1))
+            mixed_qkv_spec = rearrange(mixed_qkv_spec, 'b l d -> b d l')
+            mixed_qkv_spec = causal_conv1d_update(
+                mixed_qkv_spec,
+                conv_state,
+                conv_weights,
+                self.conv1d.bias,
+                self.activation,
+                conv_state_indices=spec_state_indices_tensor[:, 0]
+                [:attn_metadata.num_spec_decodes],
+                num_accepted_tokens=num_accepted_tokens,
+                validate_data=False,
+            )
+            mixed_qkv_spec = rearrange(mixed_qkv_spec, 'b d l -> (b l) d')
+
         # 2.2: process the remaining part
         if attn_metadata.num_prefills > 0:
             # - "cache_indices" updates the conv_state cache in positions