fix crash if gaudi_config is not passed to GaudiTrainer, only gaudi_c…

[sywangyi]

…onfig_name is passed in training args.

What does this PR do?

Fixes # (issue)

Before submitting

• This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
• Did you make sure to update the documentation with your changes?
• Did you write any new necessary tests?

[sywangyi]

call stack like
Traceback (most recent call last):
File "/intel-extension-for-transformers/optimum-habana/examples/language-modeling/run_clm.py", line 697, in
main()
File "/intel-extension-for-transformers/optimum-habana/examples/language-modeling/run_clm.py", line 625, in main
trainer = GaudiTrainer(
File "/intel-extension-for-transformers/optimum-habana/optimum/habana/transformers/trainer.py", line 217, in init
gaudi_config.declare_autocast_bf16_fp32_ops()
AttributeError: 'NoneType' object has no attribute 'declare_autocast_bf16_fp32_ops'

[HuggingFaceDocBuilderDev]

The docs for this PR live here. All of your documentation changes will be reflected on that endpoint. The docs are available until 30 days after the last update.

[regisss]

Good catch!