morello: Add Morello platform documentation

Morello platform has a SCP which brings the primary Rainier CPU
out of reset which starts executing at BL31.

This patch provides documentation support for Morello platform.

Signed-off-by: Chandni Cherukuri <chandni.cherukuri@arm.com>
Change-Id: I38f596668e2b14862d543fabc04549ff34bfb8a2
2 files changed