fix(rmmd): add missing padding to RMM Boot Manifest and initialize it

This patch also:
     * Enforces the check of RES0 fields on EL3-RMM boot interface
       and manifest
     * Fixes a couple of nits on the EL3-RMM Boot Interface
       documentation.

Signed-off-by: Javier Almansa Sobrino <javier.almansasobrino@arm.com>
Change-Id: Idb9e38f9fcda2ba0655646a1e2c4fdbabd5cdc40
7 files changed