MdeModulePkg: SmbiosDxe: ARM and AARCH64 are VALID_ARCHITECTURES

MdeModulePkg: SmbiosDxe: ARM and AARCH64 are VALID_ARCHITECTURES

This driver is soon going to be built by ArmVirtPkg/ArmVirtQemu.dsc
(without any changes). Although VALID_ARCHITECTURES is not used by the
build system (it is just a comment), it is best kept up-to-date for human
readers' sake.

Cc: Feng Tian <feng.tian@intel.com>
Cc: Elvin Li <elvin.li@intel.com>
Cc: Star Zeng <star.zeng@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Star Zeng <star.zeng@intel.com>
Reviewed-by: Feng Tian <feng.tian@intel.com>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@18041 6f19259b-4bc3-4df7-8a09-765794883524