[Bugfix][P/D] fix layerwise connector for decoder tp size > num kv heads (#5846)

### What this PR does / why we need it?
Fix layerwise connector for decoder tp size > num kv heads. In this case
prefiller should push kv cache to all decoder npu.

- vLLM version: v0.13.0
- vLLM main:
2f4e6548ef

Signed-off-by: liziyu <liziyu16@huawei.com>

vllm_ascend/distributed/mooncake_layerwise_connector.py

@@ -1078,10 +1078,14 @@ class MooncakeLayerwiseConnectorWorker:
         ):
             # enable decode prefix cache
             if self.use_mla or self.use_sparse:
-                num_kv_head = self._decode_tp_size
+                num_need_send = self._decode_tp_size
             else:
                 num_kv_head = self.vllm_config.model_config.hf_config.num_key_value_heads
-            num_replica_groups = self.tp_size // num_kv_head if self.tp_size >= num_kv_head else 1
+                if self.tp_size <= num_kv_head:
+                    num_need_send = self.tp_size
+                else:
+                    num_need_send = self._decode_tp_size if self._decode_tp_size >= num_kv_head else num_kv_head
+            num_replica_groups = self.tp_size // num_need_send if self.tp_size >= num_need_send else 1
             replica_group_idx = self.tp_rank % num_replica_groups
             req_ids = sorted(list(connector_metadata.requests.keys()))
             selected_req_ids = [