[llvm] [AMDGPU][GlobalISel] Fix issue with copy_scc_vcc on gfx7 (PR #165355)

[Petar Avramovic via llvm-commits]

petar-avramovic wrote:

> > Also could we do the OR on newer targets also?
> 
> Won't that waste an SGPR in some cases, since we need to allocate one for the dead dest of the OR?

True, @vangthao95 can you restore use of compare on new targets

https://github.com/llvm/llvm-project/pull/165355