[X86][AVX512] Added VPSLLDQ/VPSRLDQ memory fold tests

Memory operand is new for AVX512 (SSE/AVX2 didn't support it).

Also dropped the 'mask' from the tests (VPSLLDQ/VPSRLDQ don't support masked operations).

Regenerated VPALIGNR test now that the shuffle comments work

llvm-svn: 272383