arm64: Add feature detection for fine grained traps

In order to allow us to have shared code for managing fine grained traps
for KVM guests add it as a detected feature rather than relying on it
being a dependency of other features.

Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
[maz: converted to ARM64_CPUID_FIELDS()]
Link: https://lore.kernel.org/r/20230301-kvm-arm64-fgt-v4-1-1bf8d235ac1f@kernel.org


Reviewed-by: Zenghui Yu <yuzenghui@huawei.com>
Reviewed-by: Miguel Luis <miguel.luis@oracle.com>
Reviewed-by: Jing Zhang <jingzhangos@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20230815183903.2735724-10-maz@kernel.org