[ARM] Cleanup part of ARMBaseInstrInfo::optimizeCompareInstr (NFCI).

As noted in another review, this loop is confusing.  This commit cleans it up
somewhat.

Differential Revision: https://reviews.llvm.org/D42312

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@323136 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed