### What this PR does / why we need it? When enable VLLM_ASCEND_FLASHCOMM2_PARALLEL_SIZE>1, we need index operation to reorganize the batch, because that we need ensure the correct batch-id for each rank after the reduce-scatter op in VLLM_ASCEND_FLASHCOMM2_PARALLEL_SIZE>1. But we do not need it when VLLM_ASCEND_FLASHCOMM2_PARALLEL_SIZE=1, which dose not need reduce-scatter. Signed-off-by: Levi-JQ <yujinqi2@huawei.com> Co-authored-by: Levi-JQ <yujinqi2@huawei.com>