feat(rmmd): add support to create a boot manifest

This patch also adds an initial RMM Boot Manifest (v0.1) for fvp
platform.

Signed-off-by: Javier Almansa Sobrino <javier.almansasobrino@arm.com>
Change-Id: I1374f8f9cb207028f1820953cd2a5cf6d6c3b948