This patch adds support for the TM2 touch key and led functionality.

The driver interfaces with userspace through an input device and reports
KEY_PHONE and KEY_BACK event types. LED brightness can be controlled by
"/sys/class/leds/tm2-touchkey/brightness".
Signed-off-by: NBeomho Seo <beomho.seo@samsung.com>
Signed-off-by: NJaechul Lee <jcsing.lee@samsung.com>
Reviewed-by: NJavier Martinez Canillas <javier@osg.samsung.com>
Reviewed-by: NAndi Shyti <andi.shyti@samsung.com>
Reviewed-by: NChanwoo Choi <cw00.choi@samsung.com>
Tested-by: NChanwoo Choi <cw00.choi@samsung.com>
Acked-by: NKrzysztof Kozlowski <krzk@kernel.org>
Acked-by: NRob Herring <robh@kernel.org>
Signed-off-by: NDmitry Torokhov <dmitry.torokhov@gmail.com>