[LV] Tail-folding, runtime scev checks
Now that we allow tail-folding, not only when we optimise for size, make
sure we do not run in this assert.
Differential revision: https://reviews.llvm.org/D66932
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@370711 91177308-0d34-0410-b5e6-96231b3b80d8