[Neuron] [Bugfix] Fix neuron startup (#9374)

Co-authored-by: Jerzy Zagorski <jzagorsk@amazon.com>

vllm/utils.py

@@ -327,15 +327,6 @@ def is_openvino() -> bool:
         return False
 
 
-@lru_cache(maxsize=None)
-def is_neuron() -> bool:
-    try:
-        import transformers_neuronx
-    except ImportError:
-        transformers_neuronx = None
-    return transformers_neuronx is not None
-
-
 @lru_cache(maxsize=None)
 def is_xpu() -> bool:
     from importlib.metadata import PackageNotFoundError, version
@@ -786,7 +777,7 @@ def is_pin_memory_available() -> bool:
     elif is_xpu():
         print_warning_once("Pin memory is not supported on XPU.")
         return False
-    elif is_neuron():
+    elif current_platform.is_neuron():
         print_warning_once("Pin memory is not supported on Neuron.")
         return False
     elif current_platform.is_cpu() or is_openvino():