[LoopUnroll] Fix bug in computeUnrollCount causing it to not honor MaxCount

Reviewers: sanjoy, anna, reames, apilipenko, igor-laevsky, mkuper

Subscribers: mcrosier, llvm-commits, mzolotukhin

Differential Revision: https://reviews.llvm.org/D34532

llvm-svn: 306564
2 files changed