[LVI] NFC. On the fast dest path use inverse predicate instead of inverse range result

[LVI] NFC. On the fast dest path use inverse predicate instead of inverse range result

Gathering constantins from a condition on the false path ask makeAllowedICmpRegion about inverse predicate instead of inversing the resulting range.

This change was separated from the review "[LVI] Make LVI smarter about comparisons with non-constants" (https://reviews.llvm.org/D23205#inline-198361)

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@278009 91177308-0d34-0410-b5e6-96231b3b80d8