[llvm] AMDGPU: Add baseline tests for gep flag handling (PR #110814)

[Matt Arsenault via llvm-commits]

arsenm wrote:

### Merge activity

* **Oct 9, 5:42 AM EDT**: @arsenm started a stack merge that includes this pull request via [Graphite](https://app.graphite.dev/github/pr/llvm/llvm-project/110814).


https://github.com/llvm/llvm-project/pull/110814