[llvm] AMDGPU: Fix producing invalid IR on vector typed getelementptr (PR #114113)

[Matt Arsenault via llvm-commits]

arsenm wrote:

### Merge activity

* **Oct 30, 1:12 AM EDT**: A user started a stack merge that includes this pull request via [Graphite](https://app.graphite.dev/github/pr/llvm/llvm-project/114113).


https://github.com/llvm/llvm-project/pull/114113