The Actions Semi ATC260x PMICs are able to manage an onkey button.
This driver exposes the ATC260x onkey as an input device. It can also
be configured to force a system reset on a long key-press with an
adjustable duration.

The currently supported chip variants are ATC2603C and ATC2609A.
Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@gmail.com>
Acked-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>