irqchip: renesas-irqc: Use lazy disable

Set the ->irq_enable() and ->irq_disable() methods to NULL
to enable lazy disable of interrupts. This by itself provides
some level of optimization, but is mainly enabled as ground
work for future Suspend-to-RAM wake up support.

Signed-off-by: Magnus Damm <damm@opensource.se>
Cc: rob.herring@calxeda.com
Cc: grant.likely@secretlab.ca
Cc: horms@verge.net.au
Link: http://lkml.kernel.org/r/20131204120546.29642.15772.sendpatchset@w520
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

drivers/irqchip/irq-renesas-irqc.c

@@ -212,8 +212,6 @@ static int irqc_probe(struct platform_device *pdev)
 	irq_chip->name = name;
 	irq_chip->irq_mask = irqc_irq_disable;
 	irq_chip->irq_unmask = irqc_irq_enable;
-	irq_chip->irq_enable = irqc_irq_enable;
-	irq_chip->irq_disable = irqc_irq_disable;
 	irq_chip->irq_set_type = irqc_irq_set_type;
 	irq_chip->flags	= IRQCHIP_SKIP_SET_WAKE;