[Model] enable data parallel for Llama4 vision encoder (#18368)

Signed-off-by: yzhen <yzhen@devgpu093.cco2.facebook.com>
Co-authored-by: yZhen <yZhen@fb.com>
Co-authored-by: yzhen <yzhen@devgpu093.cco2.facebook.com>

vllm/config.py

@@ -1790,6 +1790,10 @@ class ParallelConfig:
     rank: int = 0
     """Global rank in distributed setup."""
 
+    enable_multimodal_encoder_data_parallel: bool = False
+    """ Use data parallelism instead of tensor parallelism for vision encoder. 
+    Only support LLama4 for now"""
+
     @property
     def world_size_across_dp(self) -> int:
         """world_size_across_dp is TPxPPxDP, it is the size of the world