[AVX512] Remove and autoupgrade many of the broadcast intrinsics

Summary:
This autoupgrades most of the broadcast intrinsics. They've been unused in clang for some time.

This leaves the 32x2 intrinsics because they are still used in clang.

Reviewers: RKSimon, zvi, igorb

Reviewed By: RKSimon

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D36606

llvm-svn: 310725