Platform/DeveloperBox: add .DSC/.FDF description of MM components

Create a pair of .DSC/.FDF files that describe the components and
the firmware volumes and flash device that will be dispatched into
a secure partition in the secure world to control the UEFI secure
variable store.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>