[AMDGPU][llvm-mc] s_setreg* - Fix order of operands

Order should match the sp3 syntax, where destination (simm16 denoting the hwreg) is coming first.

Differential Revision: http://reviews.llvm.org/D19161

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@266617 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed