[llvm] [AMDGPU] Fix GFX1250 hazard: S_SET_VGPR_MSB dropped (PR #184904)

[Yaxun Liu via llvm-commits]

yxsamliu wrote:

> It's a huge change and hazard recognizer mitigates the hazard for instruction which does not exist yet. Why not to insert nops in the VGPR lowering pass itself?

I agree it would be much simpler to do this in the VGPR lowering pass itself. @jayfoad Shall I move the insertion of nop's to the VGPR lowering pass?

https://github.com/llvm/llvm-project/pull/184904