KVM: arm64: vgic-its: Read config and pending bit in add_lpi()

When creating the lpi we now ask the redistributor what is the state
of the LPI (priority, enabled, pending).

Signed-off-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
Reviewed-by: Christoffer Dall <cdall@linaro.org>