arm/arm64: KVM: vgic: Parametrize VGIC_NR_SHARED_IRQS

arm/arm64: KVM: vgic: Parametrize VGIC_NR_SHARED_IRQS

Having a dynamic number of supported interrupts means that we
cannot relly on VGIC_NR_SHARED_IRQS being fixed anymore.

Instead, make it take the distributor structure as a parameter,
so it can return the right value.

Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
(cherry picked from commit fb65ab63b8cae510ea1e43e68b5da2f9980aa6d5)
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>