[clang] [llvm] AMDGPU: Add v_mfma_i32_16x16x64_i8 for gfx950 (PR #116728)

[Matt Arsenault via llvm-commits]

arsenm wrote:

### Merge activity

* **Nov 21, 12:00 PM EST**: [Graphite](https://app.graphite.dev/github/pr/llvm/llvm-project/116728) rebased this pull request as part of a merge.


https://github.com/llvm/llvm-project/pull/116728