ARM: dts: ux500: add synaptics RMI4 for Ux500 TVK DT

This adds the Synaptics RMI4 touchscreen to the Ux500 TVK
user interface board. Tested on the U8500 HREFv60plus with
the TVK UIB.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Olof Johansson <olof@lixom.net>