KVM: arm/arm64: vgic: Introduce find_reg_by_id()

In order to implement vGICv3 CPU interface access, we will need to perform
table lookup of system registers. We would need both index_to_params() and
find_reg() exported for that purpose, but instead we export a single
function which combines them both.

Signed-off-by: Pavel Fedin <p.fedin@samsung.com>
Signed-off-by: Vijaya Kumar K <Vijaya.Kumar@cavium.com>
Reviewed-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Acked-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>