Override read values from feature ID registers to reflect Hafnium support

Hafnium limits access to certain features to certain or to all VMs. When
querying available features in feature ID registers, the returned result should
reflect the supported features.

Reorganize how features are trapped so that the logic can be controlled in one
place rather than being spread out throughout the code.

Bug: 144415253
Bug: 144898870
Change-Id: Id13fdcd3fd50beb70bbd51a3de15e2c5e1003eb6
14 files changed