[X86] Replace avx2 broadcast intrinsics with native IR.

[X86] Replace avx2 broadcast intrinsics with native IR.

Since r245605, the clang headers don't use these anymore.
r245165 updated some of the tests already; update the others, add
an autoupgrade, remove the intrinsics, and cleanup the definitions.

Differential Revision: http://reviews.llvm.org/D10555

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@245606 91177308-0d34-0410-b5e6-96231b3b80d8