MdePkg/BaseMemoryLibOptDxe: Apply BSD-2-Clause-Patent

Change license to BSD-2-Clause-Patent using an
SPDX-License-Identifier statement.

Cc: Liming Gao <liming.gao@intel.com>
Cc: Leif Lindholm <leif@nuviainc.com>
Cc: Ard Biesheuvel <ard.biesheuvel@arm.com>
Signed-off-by: Michael D Kinney <michael.d.kinney@intel.com>
Reviewed-by: Leif Lindholm <leif@nuviainc.com>
Acked-by: Ard Biesheuvel <ard.biesheuvel@arm.com>