R600/SI: Various instruction format bit test cleanups

- Fix missing SALU format bits
- Remove unused isSALUInstr
- Add isVALU
- Switch isDS to use a bit like the others
- Move SIInstrInfo::is* functions to header
- Reorder so they are approximately sorted by type (SALU, VALU, memory)

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@223038 91177308-0d34-0410-b5e6-96231b3b80d8