[llvm] AMDGPU: Avoid creating unnecessary block split in atomic expansion (PR #102440)

[Matt Arsenault via llvm-commits]

arsenm wrote:

### Merge activity

* **Aug 8, 4:33 PM EDT**: @arsenm started a stack merge that includes this pull request via [Graphite](https://app.graphite.dev/github/pr/llvm/llvm-project/102440).


https://github.com/llvm/llvm-project/pull/102440