[X86][AVX512DQ] Move v2i64 and v4i64 MUL lowering to tablegen

As suggested by @igorb on D26011

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@285313 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed