Input: axp20x-pek - add wakeup support

At least on devices with the AXP288 PMIC the device is expected to
wakeup from suspend when the power-button gets pressed, add support
for this.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>