[llvm] [AMDGPU] Preserve live SCC when shrinking disjoint S_OR_B32 to S_ADDK_I32 (PR #228025)

[Iasonas Karaprodromidis via llvm-commits]

Iasonaskrpr wrote:

This LGTM but I think @arsenm should weigh in before merging, since he is far more experienced than I am.

https://github.com/llvm/llvm-project/pull/228025