Revert r242990: "AVX-512: Implemented encoding , DAG lowering and ..."

This commit broke the build. Numerous build bots broken, and it was
blocking my progress so reverting.

It should be trivial to reproduce -- enable the BPF backend and it
should fail when running llvm-tblgen.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@242992 91177308-0d34-0410-b5e6-96231b3b80d8
17 files changed