### What this PR does / why we need it? the multistream moe in tochari only validate in decode, but can't be applied to chunked prefill, So add some judgments to isolate the scenario ### Does this PR introduce _any_ user-facing change? No ### How was this patch tested? - vLLM version: v0.11.0rc3 - vLLM main: https://github.com/vllm-project/vllm/commit/v0.11.0 Signed-off-by: hust17yixuan <303660421@qq.com>