[bugfix] adapt to new implemented get_kv_cache_spec in cpuoffload connector (#4311)

### What this PR does / why we need it?
func `get_kv_cache_spec` in model_runner changed a lot and caused error
in cpuoffloading connector which is copied from model_runner, this PR
adapts to new implemented `get_kv_cache_spec` to fix it.

### How was this patch tested?

- vLLM version: v0.11.0
- vLLM main:
2918c1b49c

Signed-off-by: lidenghui <lidenghui1110@gmail.com>

vllm_ascend/distributed/cpu_offload_manager/metadata.py

@@ -12,7 +12,7 @@ from vllm.config import KVTransferConfig, VllmConfig
 from vllm.logger import logger
 from vllm.utils.network_utils import make_zmq_socket
 from vllm.utils.torch_utils import get_dtype_size
-from vllm.v1.kv_cache_interface import AttentionSpec
+from vllm.v1.kv_cache_interface import AttentionSpec, MLAAttentionSpec
 
 from vllm_ascend.distributed.cpu_offload_manager.cpu_kv_cache_manager import \
     CPUKVCacheManager
@@ -140,14 +140,15 @@ class MetadataServer:
             layer.page_size_bytes == any.page_size_bytes
             for any in kv_cache_specs.values()
         ])
+        use_mla = isinstance(layer, MLAAttentionSpec)
         # mla shares the same kv cache among different tp
-        if layer.use_mla:
+        if use_mla:
             tp_rank = 0
         if (pp_rank, tp_rank) in self.shared_memory:
             return self.shared_memory[(pp_rank, tp_rank)]
         available_memory = self.available_memory
         shared_memory_dict = {}
-        if layer.use_mla:
+        if use_mla:
             available_memory //= self.pipeline_parallel_size
             available_memory //= len(kv_cache_specs)
             num_blocks = available_memory // layer.page_size_bytes
@@ -165,7 +166,7 @@ class MetadataServer:
             shared_memory_dict[
                 layer_name] = MetadataServer._safe_create_shared_memory(
                     f"cpu_kv_cache_{pp_rank}_{tp_rank}_{layer_name}", nbytes)
-        if layer.use_mla:
+        if use_mla:
             assert mla_config is not None
             assert layer.head_size == mla_config.rope_dim + mla_config.nope_dim
             self.shared_memory[(pp_rank,