irqdomain: Export irq_domain_disconnect_hierarchy()

Export irq_domain_disconnect_hierarchy() so irqchip module drivers
can use it.

Signed-off-by: Maulik Shah <mkshah@codeaurora.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/1629705880-27877-2-git-send-email-mkshah@codeaurora.org