[llvm] AMDGPU: Remove m0 classes (PR #161758)

[Stanislav Mekhanoshin via llvm-commits]

rampitec wrote:

1) I wish we could get rid of it, but that is over and over again when we query an RC for get and get null. Will this happen again for M0?
2) Can we get rid of all the mir tests which test value for inline asm constraints? I am growing tired of calculating this.

https://github.com/llvm/llvm-project/pull/161758