[clang] [llvm] AMDGPU: Add v_smfmac_f32_32x32x64_bf8_bf8 for gfx950 (PR #117256)

[Matt Arsenault via llvm-commits]

arsenm wrote:

### Merge activity

* **Nov 22, 2:45 PM EST**: A user started a stack merge that includes this pull request via [Graphite](https://app.graphite.dev/github/pr/llvm/llvm-project/117256).


https://github.com/llvm/llvm-project/pull/117256