[SCEV] Rely on ConstantRange instead of custom logic; NFCI

This was first landed in rL283058 and subsequenlty reverted since a
change this depends on (rL283057) was buggy and had to be reverted.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@283079 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed