[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/kernel/irq-rm7000.c b/arch/mips/kernel/irq-rm7000.c
index 121da38..6b54c71 100644
--- a/arch/mips/kernel/irq-rm7000.c
+++ b/arch/mips/kernel/irq-rm7000.c
@@ -71,7 +71,7 @@
 		unmask_rm7k_irq(irq);
 }
 
-static hw_irq_controller rm7k_irq_controller = {
+static struct irq_chip rm7k_irq_controller = {
 	.typename = "RM7000",
 	.startup = rm7k_cpu_irq_startup,
 	.shutdown = rm7k_cpu_irq_shutdown,