Refactor: Simplify boolean conditional return statements in lib/Transforms/ObjCARC

Summary: Use clang-tidy to simplify boolean conditional return statements

Reviewers: craig.topper, bkramer, chandlerc, gottesmm

Subscribers: llvm-commits

Patch by Richard Thomson!

Differential Revision: http://reviews.llvm.org/D9999

llvm-svn: 256502