KVM: arm64: Switch to table-driven FGU configuration

KVM: arm64: Switch to table-driven FGU configuration

Defining the FGU behaviour is extremely tedious. It relies on matching
each set of bits from FGT registers with am architectural feature, and
adding them to the FGU list if the corresponding feature isn't advertised
to the guest.

It is however relatively easy to dump most of that information from
the architecture JSON description, and use that to control the FGU bits.

Let's introduce a new set of tables descripbing the mapping between
FGT bits and features. Most of the time, this is only a lookup in
an idreg field, with a few more complex exceptions.

While this is obviously many more lines in a new file, this is
mostly generated, and is pretty easy to maintain.

Reviewed-by: Joey Gouly <joey.gouly@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>