fix inplace modification error by adding clone()
# What does this PR do?
When using `DistributedDataParallel`, `token_type_embedding` may occur RuntimeError: one of the variables needed for gradient computation has been modified by an inplace operation:

<img width="1791" alt="image" src="https://user-images.githubusercontent.com/19511788/177119562-1c341b15-da7b-474e-a1dd-f5f68f843142.png">

This is because of inplace operation at `buffered_token_type_ids = self.embeddings.token_type_ids[:, :seq_length]` so I just added `.clone()` to solve it as follows.

from (original)
```python
if token_type_ids is None:
    if hasattr(self.embeddings, "token_type_ids"):
        buffered_token_type_ids = self.embeddings.token_type_ids[:, :seq_length]
        buffered_token_type_ids_expanded = buffered_token_type_ids.expand(batch_size, seq_length)
        token_type_ids = buffered_token_type_ids_expanded
```

to
```python
if token_type_ids is None:
    if hasattr(self.embeddings, "token_type_ids"):
        buffered_token_type_ids = self.embeddings.token_type_ids[:, :seq_length]
        buffered_token_type_ids_expanded = buffered_token_type_ids.expand(batch_size, seq_length)
        token_type_ids = buffered_token_type_ids_expanded.clone()
```

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- [ ] Did you write any new necessary tests?


## Who can review?
@LysandreJik
_The documentation is not available anymore as the PR was closed or merged._<|||||>Do you have a reproducible code example that raises this error? cc @sgugger @patrickvonplaten <|||||>@LysandreJik I found the problem is in DistributedDataParallel not transformers. I fixed the problem. Sorry to take your time!