KVM: arm64: Propagate and handle Fine-Grained UNDEF bits

KVM: arm64: Propagate and handle Fine-Grained UNDEF bits

In order to correctly honor our FGU bits, they must be converted
into a set of FGT bits. They get merged as part of the existing
FGT setting.

Similarly, the UNDEF injection phase takes place when handling
the trap.

This results in a bit of rework in the FGT macros in order to
help with the code generation, as burying per-CPU accesses in
macros results in a lot of expansion, not to mention the vcpu->kvm
access on nvhe (kern_hyp_va() is not optimisation-friendly).

Reviewed-by: Joey Gouly <joey.gouly@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20240214131827.2856277-19-maz@kernel.org
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>