Fix minor build issue (NFC)

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.

Differential Revision: https://reviews.llvm.org/D94415