[X86][AVX512] Fix sext v32i1 -> v32i8 lowering.
Fix PR30600.

Differential Revision: https://reviews.llvm.org/D25554

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@284134 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed