[NLP] Use helpers from utils_funcs.py in Llama conversion

[janekl]

What does this PR do ?

An improvement to use torch_dtype_from_precision helper to resolve precision.

Collection: [NLP]

Jenkins CI

To run Jenkins, a NeMo User with write access must comment jenkins on the PR.

Before your PR is "Ready for review"

Pre checks:

• Make sure you read and followed Contributor guidelines
• Did you write any new necessary tests?
• Did you add or update any necessary documentation?
• Does the PR affect components that are optional to install? (Ex: Numba, Pynini, Apex etc)
  • Reviewer: Does the PR have correct import guards for all optional libraries?

PR Type:

• Improvement

Who can review?

Anyone in the community is free to review the PR once the checks have passed.
Contributor guidelines contains specific people who can review PRs to various areas.

Additional Information

• Related to [NLP] HF -> NeMo conversion enhancements #7935

[ericharper]

LGTM. Thanks!