[StackSlotColoring] Use Register for isLoadFromStackSlot/isStoreToStackSlot result. NFC

Author: topperc

llvm/lib/CodeGen/StackSlotColoring.cpp

@@ -472,8 +472,8 @@ bool StackSlotColoring::RemoveDeadStores(MachineBasicBlock* MBB) {
     MachineBasicBlock::iterator NextMI = std::next(I);
     MachineBasicBlock::iterator ProbableLoadMI = I;
 
-    unsigned LoadReg = 0;
-    unsigned StoreReg = 0;
+    Register LoadReg;
+    Register StoreReg;
     unsigned LoadSize = 0;
     unsigned StoreSize = 0;
     if (!(LoadReg = TII->isLoadFromStackSlot(*I, FirstSS, LoadSize)))