[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/vr41xx/common/irq.c b/arch/mips/vr41xx/common/irq.c
index 66aa508..965f3d6 100644
--- a/arch/mips/vr41xx/common/irq.c
+++ b/arch/mips/vr41xx/common/irq.c
@@ -62,7 +62,7 @@
 static void irq_dispatch(unsigned int irq, struct pt_regs *regs)
 {
 	irq_cascade_t *cascade;
-	irq_desc_t *desc;
+	struct irq_desc *desc;
 
 	if (irq >= NR_IRQS) {
 		atomic_inc(&irq_err_count);