[llvm] [AMDGPU] Add scheduling stage to rewrite MFMA from VGPR to AGPR (PR #149367)

[Jeffrey Byrnes via llvm-commits]

jrbyrnes wrote:

force-push to bring in https://github.com/llvm/llvm-project/pull/150711 -- this PR is required in order for the heuristic to work, otherwise we see tons of excess ArchVGPR RP even in the cases where ArchVGPR pressure is fine.

https://github.com/llvm/llvm-project/pull/149367