R600/SI: Don't run SI passes on R600 subtargets

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@223252 91177308-0d34-0410-b5e6-96231b3b80d8
R600/SI: Move SIInsertWaits into AMDGPUPassConfig::addPreSched2()

This pass needs to be run after PrologEpilogInserter, because
that pass may inserter spill code which reads or writes memory.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@223253 91177308-0d34-0410-b5e6-96231b3b80d8