[mips] More range-based for loops. NFC.

There are still a couple more inside the MIPS target. I opted for a single
commit in order to avoid spamming the list.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@266472 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed