[AMDGPU][MC] Added missing VOP3P opcodes

Added support of the following opcodes:
  v_pk_sub_u16
  v_pk_mad_i16
  v_pk_mad_u16

See Bug 33593: https://bugs.llvm.org//show_bug.cgi?id=33593

Reviewers: vpykhtin, artem.tamazov, arsenm

Differential Revision: https://reviews.llvm.org/D34890

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@308281 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed