### What this PR does / why we need it?
The former PR https://github.com/vllm-project/vllm-ascend/pull/736
select the valid token inside the `input_ids` and `position_ids` breaks
the necessary padding required by torchair. In this PR, we pending the
pad logic after the multimodal part.
Signed-off-by: ganyi <pleaplusone.gy@gmail.com>