AMDGPU/SI: Adjust the encoding family for D16 buffer instructions when the target has UnpackedD16VMem feature.

Reviewers:
  Matt and Brian

Differential Revision:
  https://reviews.llvm.org/D42548

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@323988 91177308-0d34-0410-b5e6-96231b3b80d8
6 files changed