[llvm] [AMDGPU] Fix setreg handling in the VGPR MSB lowering (PR #186491)

[Stanislav Mekhanoshin via llvm-commits]

rampitec wrote:

> Seems like this PR is based on misunderstanding the "HasSetregVGPRMSBFixup" hardware behaviour?

To be on the safe side I am going to always create S_SET_VGPR_MSB if offset is not zero.

https://github.com/llvm/llvm-project/pull/186491