[Minor] Add logging when using MXFP4 MXFP8 TRTLLM backend (#34916)

Signed-off-by: frankwang28 <frank.wbb@hotmail.com>
Signed-off-by: Frank Wang <41319051+frankwang28@users.noreply.github.com>
Co-authored-by: Wentao Ye <44945378+yewentao256@users.noreply.github.com>

vllm/model_executor/layers/quantization/mxfp4.py

@@ -128,6 +128,9 @@ def get_mxfp4_backend(with_lora_support: bool) -> Mxfp4Backend:
             and has_flashinfer()
             and envs.VLLM_USE_FLASHINFER_MOE_MXFP4_MXFP8
         ):
+            logger.info_once(
+                "Using FlashInfer MXFP4 MXFP8 TRTLLM backend for SM100", scope="local"
+            )
             return Mxfp4Backend.SM100_FI_MXFP4_MXFP8_TRTLLM
         elif current_platform.is_device_capability_family(100) and has_flashinfer():
             logger.info_once(