irqchip: gic: Remove warning by including linux/irqdomain.h

irqchip: gic: Remove warning by including linux/irqdomain.h

Commit

  853a33ce6932 irqchip: gic-v2m: Add support for ARM GICv2m MSI(-X) doorbell

Introduced a series of warnings when building ARM multi_v7_defconfig:

  include/linux/irqchip/arm-gic.h:109:53: warning: its scope is only this definition or declaration, which is probably not what you want
  In file included from arch/arm/mach-ux500/pm.c:13:0:
  include/linux/irqchip/arm-gic.h:109:53: warning: 'struct irq_domain' declared inside parameter list
   int gicv2m_of_init(struct device_node *node, struct irq_domain *parent);
                                                       ^

Fix this by adding the proper include.

Signed-off-by: Jason Cooper <jason@lakedaemon.net>
[ jac merged much more correct version from Marc into this patch ]
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Link: https://lkml.kernel.org/r/1417170975-1163-1-git-send-email-marc.zyngier@arm.com
Signed-off-by: Jason Cooper <jason@lakedaemon.net>