ARM: dts: Add support Atmel touchpad for exynos5420-peach-pit

The Peach Pit board has an Atmel maXTouch trackpad device.
Add the needed Device Tree nodes to support it.

This Device Tree change is based on the Chrome OS 3.8 tree
but adapted to use the mainline Atmel maXTouch DT binding.

Signed-off-by: Sjoerd Simons <sjoerd.simons@collabora.co.uk>
Signed-off-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
Reviewed-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>