Adjust device logging level and add minor fixes (#41636)
This commit addresses a noisy warning and improves the robustness of the base pipeline implementation.
- The device placement message in the pipeline base class has been changed from a `warning` to a `debug` log. This reduces log noise for users who are aware of their device setup, while still providing the information for debugging purposes.
- Additionally, potential `UnboundLocalError` exceptions in the `_pad` and `check_model_type` functions have been prevented by initializing variables before their conditional assignment.
