[GlobalISel] Propagate mem operands for indexed load/stores.

There isn't a test for this yet since the combines aren't used atm, but it will
be tested as part of a future commit. I'm just making this a separate change
tidyness reasons.

Author: aemerson

llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp

@@ -1078,6 +1078,7 @@ void CombinerHelper::applyCombineIndexedLoadStore(
   MIB.addUse(MatchInfo.Base);
   MIB.addUse(MatchInfo.Offset);
   MIB.addImm(MatchInfo.IsPre);
+  MIB->cloneMemRefs(*MI.getMF(), MI);
   MI.eraseFromParent();
   AddrDef.eraseFromParent();