[AMDGPU] W/a hazard if 64 bit shift amount is a highest allocated VGPR

In this case gfx90a uses v0 instead of the correct register. Swap
the value temporarily with a lower register and then swap it back.

Unfortunately hazard recognizer works after wait count insertion,
so we cannot simply reuse an arbitrary register, hence w/a also
includes a full waitcount. This can be avoided if we run it from
expandPostRAPseudo, but that is a complete misplacement.

Differential Revision: https://reviews.llvm.org/D133067