MPAM is not handled by RMM

[javieralso-arm]

On Realm world, MPAM is disabled by EL3 Firmware (TF-A), however, if the feature is available, it will be presented to a realm, which will cause undef behavior and/or panics when the latter tries to access the feature registers.

In order to fix this issue, RMM needs:

• To hide MPAM feature to to the Realm world.
• To trap any access to MPAM registers from the Realm into RMM, so it can inject an UNDEF abort back to the realm.