ANDROID: KVM: arm64: Generalise VM features into a set of flags

We currently deal with a set of booleans for VM features,
while they could be better represented as set of flags
contained in an unsigned long, similarily to what we are
doing on the CPU side.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Bug: 209580772
Change-Id: I86be6bab12287c3eb21bbe03f255e2899edbdffb
Signed-off-by: Will Deacon <willdeacon@google.com>