mfd: Avoid unbalanced asic3 irq wakeup enables/disables

The mfd/asic3 driver does not currently define a irq_set_wake() handler.
Consequently any attempt to configure the 3 ASIC3 GPIO buttons - RECORD,
CALENDAR, HOME - as wakeup sources results in Unbalanced IRQ warnings
when the system is woken from sleep mode:

WARNING: at kernel/irq/manage.c:520 irq_set_irq_wake+0xc4/0xf8()
Unbalanced IRQ 342 wake disable
...
WARNING: at kernel/irq/manage.c:520 irq_set_irq_wake+0xc4/0xf8()
Unbalanced IRQ 337 wake disable
...
WARNING: at kernel/irq/manage.c:520 irq_set_irq_wake+0xc4/0xf8()
Unbalanced IRQ 339 wake disable
...

This patch adds a irq_set_wake() handler to the mfd/asic3 driver.

Signed-off-by: Paul Parsons <lost.distance@yahoo.com>
Cc: Philipp Zabel <philipp.zabel@gmail.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>