R600/SI: Update instruction conversions for VI

There are 3 changes:
- Convert 32-bit S_LSHL/LSHR/ASHR to their V_*REV variants for VI
- Lower RSQ_CLAMP for VI
- Don't generate MIN/MAX_LEGACY on VI

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@223604 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed