R600/SI: Enable inline assembly

We just needed to remove the assertion in
AMDGPURegisterInfo::getFrameRegister(), which is called when
initializing the parser for inline assembly.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@223197 91177308-0d34-0410-b5e6-96231b3b80d8