AMDGPU: Add AMDGPU_HS calling convention

Reviewers: arsenm, nhaehnle

Subscribers: mehdi_amini, kzhuravl, wdng, yaxunl, dstuttard, tpr, llvm-commits, t-tye

Differential Revision: https://reviews.llvm.org/D32644

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@301930 91177308-0d34-0410-b5e6-96231b3b80d8
14 files changed