[IndVars] Extract out eliminateIdentitySCEV, NFC

Summary:
Reflow a comment while at it.

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D13459

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@249470 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed