[llvm] [AMDGPU] Reland "Remove redundant s_cmp_lg_* sX, 0" (PR #164201)

[Jay Foad via llvm-commits]

https://github.com/jayfoad approved this pull request.

LGTM. Maybe wait a little in case Matt has further comments.

https://github.com/llvm/llvm-project/pull/164201