CodeGen: Use MachineInstr& in PostRAHazardRecognizer, NFC

Convert a loop to a range-based for, using MachineInstr& instead of
MachineInstr* and removing an implicit conversion from iterator to
pointer.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@274311 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed