[SVE] Eliminate calls to default-false VectorType::get() from X86

Reviewers: efriedma, sdesmalen, c-rhodes, craig.topper

Reviewed By: craig.topper

Subscribers: tschuett, hiraditya, rkruppe, psnobl, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D80331