Fix: align Qwen2.5-VL inference rope index with training by passing second_per_grid_ts
Author: Xqle
Pull request: yes

# What does this PR do?

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## Bug

In Qwen2.5-VL, during inference the method `prepare_inputs_for_generation` calls `get_rope_index` without passing `second_per_grid_ts.`
However, during training, `second_per_grid_ts` is explicitly passed.

This leads to an inconsistency between training and inference:

Training: temporal positions are scaled according to `second_per_grid_ts`.

Inference: temporal positions fall back to the default (1.0), which may cause misalignment in temporal position encoding.

## Fix

Update `prepare_inputs_for_generation` to also pass `second_per_grid_ts` to `get_rope_index.`

## Impact

Ensures temporal position encoding consistency between training and inference.

Prevents potential misalignment in multi-frame or video-based inputs.

## Related Issue
Fixes #41152 


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Comments:
**[For maintainers]** Suggested jobs to run (before merge)

run-slow: qwen2_5_vl

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