[llvm] [RISCV] Fix incorrect folding of select on ctlz/cttz (PR #155231)

[via llvm-commits]

MitchBriles wrote:

> Thanks for fixing this. Before this lands can you turn off "Keep my email address private" in your GitHub account settings? It's a developer policy so buildbots are able to notify you if something comes up with your patch: https://llvm.org/docs/DeveloperPolicy.html#id12

Done.

https://github.com/llvm/llvm-project/pull/155231