Remove the InstructionSimplifierPass immediately after InstructionCombiningPass.

InstructionCombiningPass was added after LoopUnrollPass in r237395. Because
InstructionCombiningPass is strictly more powerful than InstructionSimplifierPass,
remove the unnecessary InstructionSimplifierPass.

Differential Revision: http://reviews.llvm.org/D9838

llvm-svn: 237702