[SVE] Eliminate calls to default-false VectorType::get() from llvm-stress

Reviewers: efriedma, kmclaughlin, sdesmalen, MaskRay, JDevlieghere

Reviewed By: sdesmalen

Subscribers: tschuett, rkruppe, psnobl, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D81201