livePhysRegs: Pass MBB by reference in addLive{Ins|Outs}(); NFC

The block must no be nullptr for the addLiveIns()/addLiveOuts()
function.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@268340 91177308-0d34-0410-b5e6-96231b3b80d8
13 files changed