MIPS: lantiq: irq: register the interrupt controllers with irqchip_init

Add support for more interrupt controllers by switching from
of_irq_init() to irqchip_init() in Lantiq's arch_init_irq(). This
requires switching the ICU interrupt controller to use
IRQCHIP_DECLARE(), like a real irqchip driver would do.

This is needed for future changes when new irqchip drivers are
implemented:
- a dedicated driver for the EIU interrupt controller
- a driver for the MSI PIC (Programmable Interrupt Controller) found on
  VRX200 and newer SoCs
- ..or any other driver which uses IRQCHIP_DECLARE

Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

arch/mips/lantiq/irq.c

@@ -8,6 +8,7 @@
 #include <linux/interrupt.h>
 #include <linux/ioport.h>
 #include <linux/sched.h>
+#include <linux/irqchip.h>
 #include <linux/irqdomain.h>
 #include <linux/of_platform.h>
 #include <linux/of_address.h>
@@ -422,12 +423,9 @@ unsigned int get_c0_compare_int(void)
 	return CP0_LEGACY_COMPARE_IRQ;
 }
 
-static const struct of_device_id of_irq_ids[] __initconst = {
-	{ .compatible = "lantiq,icu", .data = icu_of_init },
-	{},
-};
+IRQCHIP_DECLARE(lantiq_icu, "lantiq,icu", icu_of_init);
 
 void __init arch_init_irq(void)
 {
-	of_irq_init(of_irq_ids);
+	irqchip_init();
 }