arm64: dmi: Add SMBIOS/DMI support

SMBIOS is important for server hardware vendors. It implements a spec for
providing descriptive information about the platform. Things like serial
numbers, physical layout of the ports, build configuration data, and the like.

Signed-off-by: Yi Li <yi.li@linaro.org>
Tested-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Tested-by: Leif Lindholm <leif.lindholm@linaro.org>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>