[llvm] [AMDGPU] Add baseline test to show spilling of wmma scale. NFC (PR #168163)

[Quentin Colombet via llvm-commits]

qcolombet wrote:

> JBTW, what happened to instnamer? It seems to cease to exist.

I can still run it with `opt -S -passes=instnamer` with my one week old build.

https://github.com/llvm/llvm-project/pull/168163