[llvm] [RISCV] Don't use EVL/Mask for vid when lowering vp.reverse (PR #123048)

[Philip Reames via llvm-commits]

preames wrote:

This sorta feels like solving the problem in the wrong place.  If the vectorizer is unprofitable emitting the vp.reverse, why not just change the vectorizer to emit a vp.reverse at vlmax or better an unpredicated vector.reverse?

https://github.com/llvm/llvm-project/pull/123048