[llvm] [AMDGPU][True16][CodeGen] fix moveToVALU with proper subreg access in true16 (PR #132089)

[Brox Chen via llvm-commits]

broxigarchen wrote:

It seems it takes more work to select t16 VALU during moveToVALU. Can be a seperate patch. Currently just fix the bad copy %2:vgpr_32 = COPY %1:vgpr_16.

Close this patch https://github.com/llvm/llvm-project/pull/131859 and proposed this alternative fix

https://github.com/llvm/llvm-project/pull/132089