[AVX512] Added load/store instructions to Register2Memory opcode tables.
Added lowering tests for load/store.

Reviewed by Elena Demikhovsky <elena.demikhovsky@intel.com>


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214972 91177308-0d34-0410-b5e6-96231b3b80d8