[llvm] [AMDGPU] Delete redundant s_or_b32 (PR #165261)

[Shilei Tian via llvm-commits]

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

Didn't realize that `s_cselect_b64` also sets SCC. LGTM.

https://github.com/llvm/llvm-project/pull/165261