[Misc] log when using default MoE config (#8971)

Author: divakar-amd

vllm/model_executor/layers/fused_moe/fused_moe.py

@@ -320,6 +320,9 @@ def get_moe_configs(E: int, N: int,
 
     # If no optimized configuration is available, we will use the default
     # configuration
+    logger.warning(
+        ("Using default MoE config. Performance might be sub-optimal! "
+         "Config file not found at %s"), config_file_path)
     return None