[AMD] Enable mamba-extra-buffer for Qwen3.5 on ROCm (#30359)

Co-authored-by: ntgiang71096 <nguyentruonggiang71096@gmail.com>

python/sglang/srt/server_args.py

@@ -4683,8 +4683,8 @@ class ServerArgs:
             view, model_arch
         ), f"extra_buffer is not supported for {model_arch}; use no_buffer."
         assert (
-            is_cuda() or is_musa() or is_npu()
-        ), "extra_buffer needs CUDA/MUSA/NPU (FLA)."
+            is_cuda() or is_musa() or is_npu() or is_hip()
+        ), "extra_buffer needs CUDA/MUSA/NPU/ROCm (FLA)."
         if view.speculative_num_draft_tokens is not None:
             assert (
                 view.mamba_radix_cache_strategy != "extra_buffer_lazy"