irqchip: GICv3: Convert to domain hierarchy

In order to start supporting stacked domains, convert the GICv3
code base to the new domain hierarchy framework, which mostly
amounts to supporting the new alloc/free callbacks.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Link: https://lkml.kernel.org/r/1416839720-18400-3-git-send-email-marc.zyngier@arm.com
Signed-off-by: Jason Cooper <jason@lakedaemon.net>