Input: gpio-keys - add support for wakeup event action

Add support for specifying event actions to trigger wakeup when using
the gpio-keys input device as a wakeup source.

This would allow the device to configure when to wakeup the system. For
example a gpio-keys input device for pen insert, may only want to wakeup
the system when ejecting the pen.

Suggested-by: Brian Norris <briannorris@chromium.org>
Signed-off-by: Jeffy Chen <jeffy.chen@rock-chips.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>