[llvm] AMDGPU: Fold copy of scalar add of frame index (PR #115058)

[Matt Arsenault via llvm-commits]

arsenm wrote:

* **#115060** <a href="https://app.graphite.dev/github/pr/llvm/llvm-project/115060?utm_source=stack-comment-icon" target="_blank"><img src="https://static.graphite.dev/graphite-32x32-black.png" alt="Graphite" width="10px" height="10px"/></a>
* **#115059** <a href="https://app.graphite.dev/github/pr/llvm/llvm-project/115059?utm_source=stack-comment-icon" target="_blank"><img src="https://static.graphite.dev/graphite-32x32-black.png" alt="Graphite" width="10px" height="10px"/></a>
* **#115058** <a href="https://app.graphite.dev/github/pr/llvm/llvm-project/115058?utm_source=stack-comment-icon" target="_blank"><img src="https://static.graphite.dev/graphite-32x32-black.png" alt="Graphite" width="10px" height="10px"/></a> 👈
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https://github.com/llvm/llvm-project/pull/115058