[CodeGen][X86] LiveRangeShrink: fix increment after end

This fixes the infinite loop discovered in #114195.
Since we skip debug instructions at the start of the loop we do not
need to skip them again at the end of the loop.

Author: MuellerMP

llvm/lib/CodeGen/LiveRangeShrink.cpp

@@ -246,7 +246,7 @@ bool LiveRangeShrink::runOnMachineFunction(MachineFunction &MF) {
         if (MI.getOperand(0).isReg())
           for (; EndIter != MBB.end() && EndIter->isDebugValue() &&
                  EndIter->hasDebugOperandForReg(MI.getOperand(0).getReg());
-               ++EndIter, ++Next)
+               ++EndIter)
             IOM[&*EndIter] = NewOrder;
         MBB.splice(I, &MBB, MI.getIterator(), EndIter);
       }