genirq: Update the comment for generic_handle_irq_desc

__do_IRQ() was removed by commit 1c77ff2 "genirq: Remove __do_IRQ",
but the comment referring to __do_IRQ() was left.

Update the comment for generic_handle_irq_desc().

Signed-off-by: Huang Shijie <shijie.huang@arm.com>
Cc: jiang.liu@linux.intel.com
Cc: peterz@infradead.org
Cc: rafael.j.wysocki@intel.com
Cc: jason@lakedaemon.net
Cc: marc.zyngier@arm.com
Link: http://lkml.kernel.org/r/1441074950-3893-1-git-send-email-shijie.huang@arm.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

include/linux/irqdesc.h

@@ -137,9 +137,7 @@ static inline struct msi_desc *irq_desc_get_msi_desc(struct irq_desc *desc)
 
 /*
  * Architectures call this to let the generic IRQ layer
- * handle an interrupt. If the descriptor is attached to an
- * irqchip-style controller then we call the ->handle_irq() handler,
- * and it calls __do_IRQ() if it's attached to an irqtype-style controller.
+ * handle an interrupt.
  */
 static inline void generic_handle_irq_desc(unsigned int irq, struct irq_desc *desc)
 {