feat(rme): add Test Realm Payload (TRP)

TRP is a small test payload that implements Realm Monitor
Management (RMM) functionalities. RMM runs in the Realm world
(R-EL2) and manages the execution of Realm VMs and their
interaction with the hypervisor in Normal world.

TRP is used to test the interface between RMM and Normal world
software, known as Realm Management Interface (RMI). Current
functions includes returning RMM version and transitioning
granules from Non-secure to Realm world and vice versa.

More information about RMM can be found at:

Signed-off-by: Zelalem Aweke <zelalem.aweke@arm.com>
Change-Id: Ic7b9a1e1f3142ef6458d40150d0b4ba6bd723ea2
11 files changed