[AMDGPU] Add v_pk_mov_b32 to supported list of unpackable instructions

[jrbyrnes]

c256966 added some baseline functionality to unpack v_pk instructions -- by unpacking we are able to co-execute with MFMA. However, we did not support unpacking for all relevant instructions. The remaining instruction is v_pk_mov_b32

[llvmbot]

@llvm/issue-subscribers-backend-amdgpu

Author: Jeffrey Byrnes (jrbyrnes)

https://github.com/llvm/llvm-project/commit/c256966fe2129ef75c76a4cab454b35ffa9410f3 added some baseline functionality to unpack v_pk instructions -- by unpacking we are able to co-execute with MFMA. However, we did not support unpacking for all relevant instructions. The next priority instructions are the v_cvt_*pk instructions. TII->isNeverCoissue contains the relevant instructions for MI300, there may be additional instructions of interest for MI350. It is important to unpack these as these often occur in MFMA hot loops.