[Bugfix] disable allreduce_rms_fusion by default when pp size > 1 (#35424)

Signed-off-by: zjy0516 <riverclouds.zhu@qq.com>

vllm/config/vllm.py

@@ -126,6 +126,9 @@ def enable_allreduce_rms_fusion(cfg: "VllmConfig") -> bool:
         # tp-dp combination broken:
         # https://github.com/vllm-project/vllm/issues/34458
         and cfg.parallel_config.data_parallel_size == 1
+        # tp-pp combination broken:
+        # https://github.com/vllm-project/vllm/issues/35426
+        and cfg.parallel_config.pipeline_parallel_size == 1
     )