[MIPS] Eleminate interrupt migration helper use.

> #define hw_interrupt_type       irq_chip
> typedef struct irq_chip         hw_irq_controller;
> #define no_irq_type             no_irq_chip
> typedef struct irq_desc         irq_desc_t;

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
diff --git a/arch/mips/au1000/pb1200/irqmap.c b/arch/mips/au1000/pb1200/irqmap.c
index 2d49f32..f66779f 100644
--- a/arch/mips/au1000/pb1200/irqmap.c
+++ b/arch/mips/au1000/pb1200/irqmap.c
@@ -148,7 +148,7 @@
 	}
 }
 
-static struct hw_interrupt_type external_irq_type =
+static struct irq_chip external_irq_type =
 {
 #ifdef CONFIG_MIPS_PB1200
 	"Pb1200 Ext",