[AMDGPU] Use v_pk_max_f16 for fcanonicalize

Differential Revision: https://reviews.llvm.org/D37325

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@312676 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed