[Misc] Cleanup useless current_platform import (#35715)

Signed-off-by: wangxiyuan <wangxiyuan1007@gmail.com>

vllm/v1/attention/backends/fa_utils.py

@@ -55,9 +55,6 @@ elif current_platform.is_rocm():
 def get_flash_attn_version(
     requires_alibi: bool = False, head_size: int | None = None
 ) -> int | None:
-    # import here to avoid circular dependencies
-    from vllm.platforms import current_platform
-
     if current_platform.is_xpu():
         return 2
     if current_platform.is_rocm():

vllm/v1/attention/backends/flashinfer.py

@@ -374,8 +374,6 @@ class FlashInferBackend(AttentionBackend):
 
     @classmethod
     def get_required_kv_cache_layout(cls) -> KVCacheLayoutType | None:
-        from vllm.platforms import current_platform
-
         capability = current_platform.get_device_capability()
         if capability is not None and capability.major == 10:
             return "HND"