refactor(mla_cp): remove unused layer_name parameter from _forward_prefill method

Signed-off-by: F.Liu <1661888967@qq.com>

Author: ader47

vllm_ascend/attention/context_parallel/mla_cp.py

@@ -505,12 +505,9 @@ def _forward_prefill(
         value: torch.Tensor,
         kv_c_and_k_pe_cache: tuple[torch.Tensor],
         attn_metadata: AscendMLAMetadata,
-        layer_name,
     ) -> torch.Tensor:
         if not self.pcp_size > 1:
-            return super()._forward_prefill(
-                q_nope, q_pe, k_nope, k_pe, value, kv_c_and_k_pe_cache, attn_metadata, layer_name
-            )
+            return super()._forward_prefill(q_nope, q_pe, k_nope, k_pe, value, kv_c_and_k_pe_cache, attn_metadata)
         assert attn_metadata.prefill is not None
         assert attn_metadata.prefill.pcp_metadata is not None
         num_tokens = q_nope.size(0)