arm64/vmm: Set and use the fine-grained traps

[andrew]

Summary

Set the Fine-grained trap registers to trap any features we don't
support. These are expected to be more useful when we support nested
virtualisation, so for now just the base features and GICv3 are not
trapped.

As nested virtualisation will require VHE we only set the fine-grained
trap registers when VHE is used.

Sponsored by: Arm Ltd