[llvm] [AMDGPU] Emit b32 movs if (a)v_mov_b64_pseudo dest vgprs are misaligned (PR #160547)

[Matt Arsenault via llvm-commits]

arsenm wrote:

> As far as I can tell there is no bug here, and if there was a bug it would be in whatever created V_MOV_B64_PSEUDO with unaligned VGPRs in the first place.

V_MOV_B64_PSEUDO should support unaligned registers, any change should be to relax the restriction 

https://github.com/llvm/llvm-project/pull/160547