Revert "CodeGen: MachineInstr::getIterator() => getInstrIterator(), NFC"

This reverts commit r261504, since it's not obvious the new name is
better:
http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20160222/334298.html

I'll recommit if we get consensus that it's the right direction.

llvm-svn: 261567

llvm/lib/CodeGen/DFAPacketizer.cpp

@@ -198,7 +198,7 @@ VLIWPacketizerList::~VLIWPacketizerList() {
 void VLIWPacketizerList::endPacket(MachineBasicBlock *MBB, MachineInstr *MI) {
   if (CurrentPacketMIs.size() > 1) {
     MachineInstr *MIFirst = CurrentPacketMIs.front();
-    finalizeBundle(*MBB, MIFirst->getInstrIterator(), MI->getInstrIterator());
+    finalizeBundle(*MBB, MIFirst->getIterator(), MI->getIterator());
   }
   CurrentPacketMIs.clear();
   ResourceTracker->clearResources();