[SCEV] Factor out isKnownViaInduction. NFC.

This just extracts the isKnownViaInduction from isKnownPredicate.

Reviewers: sanjoy, mkazantsev, reames
Reviewed By: mkazantsev
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D44554


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@327824 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed