Add new platform to support RME arch extension

    This change introduces a new platform 'aemfvp-a-rme' which builds a
    stack that supports the Realm Management Extension for Arm
    Confidential Compute Architecture.

Signed-off-by: Nuno Lopes <nuno.lopes@arm.com>
Change-Id: Ib37b06069c3b81c9439601b10c520cfd84f707f4