MIPS: Add new end of interrupt functionality for GIC.

Each platform should define its own 'gic_finish_irq' function.
Signed-off-by: NSteven J. Hill <sjhill@mips.com>

arch/mips/kernel/irq-gic.c

@@ -195,7 +195,7 @@ static struct irq_chip gic_irq_controller = {
 	.irq_mask		=	gic_mask_irq,
 	.irq_mask_ack		=	gic_mask_irq,
 	.irq_unmask		=	gic_unmask_irq,
-	.irq_eoi		=	gic_unmask_irq,
+	.irq_eoi		=	gic_finish_irq,
 #ifdef CONFIG_SMP
 	.irq_set_affinity	=	gic_set_affinity,
 #endif