[Frontend] Improve the performance of `is_reasoning_end` (#25735)

Signed-off-by: chaunceyjiang <chaunceyjiang@gmail.com>

vllm/reasoning/basic_parsers.py

@@ -59,7 +59,8 @@ class BaseThinkingReasoningParser(ReasoningParser):
             )
 
     def is_reasoning_end(self, input_ids: list[int]) -> bool:
-        return self.end_token_id in input_ids
+        end_token_id = self.end_token_id
+        return any(input_id == end_token_id for input_id in reversed(input_ids))
 
     def extract_content_ids(self, input_ids: list[int]) -> list[int]:
         """