[MM][Bugfix] Update hf_config to hf_text_config (#5319)

### What this PR does / why we need it?

Following https://github.com/vllm-project/vllm-ascend/pull/5205, update
`hf_config` to `hf_text_config`.

Find more details at
https://github.com/vllm-project/vllm-ascend/pull/5205#issuecomment-3675417534
and
https://github.com/vllm-project/vllm-ascend/pull/5205#issuecomment-3677920872.

### Does this PR introduce _any_ user-facing change?

### How was this patch tested?

- vLLM version: release/v0.13.0
- vLLM main:
5fbfa8d9ef

Signed-off-by: shen-shanshan <467638484@qq.com>

vllm_ascend/platform.py

@@ -174,7 +174,8 @@ class NPUPlatform(Platform):
                          ) if not isinstance(ascend_compilation_config, dict)
                     else ascend_compilation_config)
 
-        elif model_config and hasattr(model_config.hf_config, "index_topk"):
+        elif model_config and hasattr(model_config.hf_text_config,
+                                      "index_topk"):
             vllm_config.cache_config.cache_dtype = str(
                 model_config.dtype).replace("torch.", "")
         if model_config is None: