[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/__init__.py

@@ -35,6 +35,10 @@ def register_model():
         "PanguProMoEForCausalLM",
         "vllm_ascend.torchair.models.torchair_pangu_moe:PanguProMoEForCausalLM"
     )
+
     ModelRegistry.register_model(
         "Qwen3NextForCausalLM",
         "vllm_ascend.models.qwen3_next:CustomQwen3NextForCausalLM")
+
+    ModelRegistry.register_model(
+        "Qwen3NextMTP", "vllm_ascend.models.qwen3_next_mtp:CustomQwen3NextMTP")