Fix for the issue of device-id getting hardcoded for token_type_ids during Tracing for ConvBert
# What does this PR do?

This PR is part of a series of PRs that follows PR #11252 and applies similar changes to ConvBert.

Fixes # (issue) 
Registering a buffer for token_type_ids in the constructor and then resizing it in the forward method based on input-shape.

## Before submitting
- [ ] This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
- [X] Did you read the [contributor guideline](https://github.com/huggingface/transformers/blob/master/CONTRIBUTING.md#start-contributing-pull-requests),
      Pull Request section?
- [ X] Was this discussed/approved via a Github issue or the [forum](https://discuss.huggingface.co/)? Please add a link
      to it if that's the case. issues #5664 and #976
- [ ] Did you make sure to update the documentation with your changes? Here are the
      [documentation guidelines](https://github.com/huggingface/transformers/tree/master/docs), and
      [here are tips on formatting docstrings](https://github.com/huggingface/transformers/tree/master/docs#writing-source-documentation).
- [ ] Did you write any new necessary tests? Not required.


## Who can review?
@LysandreJik
