[llvm] [AMDGPU] Remove s_delay_alu for VALU->SGPR->SALU (PR #127212)

[Nicolai Hähnle via llvm-commits]

https://github.com/nhaehnle commented:

I'm not sure what longestWait does; and lastSgprWrite should really be lastSgprWriteFromVALU, right?

https://github.com/llvm/llvm-project/pull/127212