[llvm] VectorUtils: mark lrint, llrint as trivially vectorizable (PR #69945)

[Ramkumar Ramachandra via llvm-commits]

artagnon wrote:

As the pre-commit tests have all landed, it should now be possible to review this patch independently.

@davemgreen Thanks; fixed now.

https://github.com/llvm/llvm-project/pull/69945