[llvm] AMDGPU: Add baseline v_med3_f32 tests from minimumnum/maximumnum (PR #141047)

[Matt Arsenault via llvm-commits]

arsenm wrote:

### Merge activity

* **May 22, 6:57 PM UTC**: A user started a stack merge that includes this pull request via [Graphite](https://app.graphite.dev/github/pr/llvm/llvm-project/141047).


https://github.com/llvm/llvm-project/pull/141047