Have MachineRegisterInfo take and store the MachineFunction it
was created for rather than the TargetMachine since we only
needed the TM for the subtarget and we can get that from the
MF.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215432 91177308-0d34-0410-b5e6-96231b3b80d8