R600: Drop use of cached TargetMachine in R600InstrInfo.cpp

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210868 91177308-0d34-0410-b5e6-96231b3b80d8
R600: Move AMDGPUInstrInfo from AMDGPUTargetMachine into AMDGPUSubtarget

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210869 91177308-0d34-0410-b5e6-96231b3b80d8