Revert "AMDGPU: Add VI i16 support"

This reverts commit r285939 and r285948.  These broke some conformance tests.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@285995 91177308-0d34-0410-b5e6-96231b3b80d8
42 files changed