[Feat] Shared expert dp for deepseek and deepseek_mtp (#3495)

### What this PR does / why we need it?
shared expert dp for deepseek and deepseek_mtp, could be combined with
sp to improve performance.

### How was this patch tested?

- vLLM version: v0.11.0rc3
- vLLM main: https://github.com/vllm-project/vllm/commit/v0.11.0

---------

Signed-off-by: zhaozx-cn <zhaozx2116@163.com>
Co-authored-by: realliujiaxu <realliujiaxu@163.com>

vllm_ascend/models/layers/mla.py

@@ -122,8 +122,17 @@ class AscendMultiHeadLatentAttention(MultiHeadLatentAttention):
             hidden_states: torch.Tensor,
             kv_cache: Optional[torch.Tensor] = None,
             attn_metadata: Optional[AttentionMetadata] = None) -> torch.Tensor:
-        need_gather_q_kv = get_forward_context().sp_enabled
-        output_shape = hidden_states.shape
+        forward_context = get_forward_context()
+        sp_enabled = forward_context.sp_enabled
+        need_gather_q_kv = False
+        if sp_enabled and self.debug_layer_idx < self.layers:
+            need_gather_q_kv = True
+        if not sp_enabled or self.debug_layer_idx < self.layers:
+            output_shape = hidden_states.shape
+        else:
+            # used in deepseek mtp layer
+            output_shape = torch.chunk(hidden_states, self.tp_size,
+                                       dim=0)[0].shape
         # FIXME: This does not seem right, should make sure the buffer is fixed
         output = torch.empty(output_shape,
                              dtype=hidden_states.dtype,