[LoopIdiomRecognize] Remove unnecessary cast from BinaryOperator to Instruction. NFC

BinaryOperator is a sub class of Instruction. We don't need an explicit cast back to Instruction.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@331432 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed