Fix XLA fp16 and bf16 error checking (#18913)
* Fix XLA fp16 and bf16 error checking
* Update src/transformers/training_args.py
Co-authored-by: Sylvain Gugger <35901082+sgugger@users.noreply.github.com>
Co-authored-by: Sylvain Gugger <35901082+sgugger@users.noreply.github.com>