[LV] Prevent interleaving if computeMaxVF returned None.

As discussed in D57382, interleaving should be avoided if computeMaxVF
returns None, same as we currently do for vectorization.

Fixes https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=6477

Reviewers: Ayal, dcaballe, hsaito, mkuper, rengolin

Reviewed By: Ayal

Differential Revision: https://reviews.llvm.org/D57837

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@353461 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed