[llvm] [AMDGPU] Reorganize tests to unblock #112403 (PR #115503)

[Shilei Tian via llvm-commits]

shiltian wrote:

### Merge activity

* **Nov 8, 12:54 PM EST**: A user started a stack merge that includes this pull request via [Graphite](https://app.graphite.dev/github/pr/llvm/llvm-project/115503).


https://github.com/llvm/llvm-project/pull/115503