Skip top_p computations when set to 1.0
jenkins jenkins jenkins
# What does this PR do ?

This avoid doing useless computations (that may even filter out some tokens due to numerical approximation) when `top_p=1.0` (which is not supposed to have any effect).

**Collection**: nlp

# Changelog 
- Skip top_p computations when set to 1.0

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**PR Type**:
- [ ] New Feature
- [ ] Bugfix
- [ ] Documentation
- [X] Optimization

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