arm64: Use irqchip_init() for interrupt controller initialisation

This patch uses the generic irqchip_init() function for initialising the
interrupt controller on arm64. It also adds several definitions required
by the ARM GIC irqchip driver but does not enable ARM_GIC yet.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
diff --git a/arch/arm64/include/asm/irq.h b/arch/arm64/include/asm/irq.h
index a4e1cad..0332fc0 100644
--- a/arch/arm64/include/asm/irq.h
+++ b/arch/arm64/include/asm/irq.h
@@ -4,5 +4,6 @@
 #include <asm-generic/irq.h>
 
 extern void (*handle_arch_irq)(struct pt_regs *);
+extern void set_handle_irq(void (*handle_irq)(struct pt_regs *));
 
 #endif