genirq: Fix documentation of default chip disable()

The documentation says that by default disable() will be
chip->mask but in fact default_disable() is a noop.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
LKML-Reference: <1262698198-30392-1-git-send-email-broonie@opensource.wolfsonmicro.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

include/linux/irq.h

@@ -90,7 +90,7 @@ struct msi_desc;
  * @startup:		start up the interrupt (defaults to ->enable if NULL)
  * @shutdown:		shut down the interrupt (defaults to ->disable if NULL)
  * @enable:		enable the interrupt (defaults to chip->unmask if NULL)
- * @disable:		disable the interrupt (defaults to chip->mask if NULL)
+ * @disable:		disable the interrupt
  * @ack:		start of a new interrupt
  * @mask:		mask an interrupt source
  * @mask_ack:		ack and mask an interrupt source