Fix minor build issue (NFC)

[dstuttard]

Summary

Change [x86] Fix tile register spill issue was causing problems for our build
using gcc-5.4.1

The problem was caused by this line:

for (const MachineInstr &MI : make_range(MIS.begin(), MI))

where MI was previously defined as a MachineBasicBlock iterator.

[rnk]

We are also observing this build breakage, so I'm going to go ahead and push this now.

[LuoYuanke]

Thank David!

llvm/lib/CodeGen/InlineSpiller.cpp

for (auto &Ent : MergeableSpills) {
     if (!SpillsToIns.empty() || !SpillsToRm.empty())
       StackIntvl.MergeValueInAsValue(OrigLI, OrigVNI,
                                      StackIntvl.getValNumInfo(0));
 
     // Insert hoisted spills.
     for (auto const &Insert : SpillsToIns) {
       MachineBasicBlock *BB = Insert.first;
       Register LiveReg = Insert.second;
-      MachineBasicBlock::iterator MI = IPA.getLastInsertPointIter(OrigLI, *BB);
-      MachineInstrSpan MIS(MI, BB);
-      TII.storeRegToStackSlot(*BB, MI, LiveReg, false, Slot,
+      MachineBasicBlock::iterator MII = IPA.getLastInsertPointIter(OrigLI, *BB);
+      MachineInstrSpan MIS(MII, BB);
+      TII.storeRegToStackSlot(*BB, MII, LiveReg, false, Slot,
                               MRI.getRegClass(LiveReg), &TRI);
-      LIS.InsertMachineInstrRangeInMaps(MIS.begin(), MI);
-      for (const MachineInstr &MI : make_range(MIS.begin(), MI))
+      LIS.InsertMachineInstrRangeInMaps(MIS.begin(), MII);
+      for (const MachineInstr &MI : make_range(MIS.begin(), MII))
         getVDefInterval(MI, LIS);
       ++NumSpills;
     }
 
     // Remove redundant spills or change them to dead instructions.
     NumSpills -= SpillsToRm.size();
     for (auto const RMEnt : SpillsToRm) {
       RMEnt->setDesc(TII.get(TargetOpcode::KILL));