ARM: at91/dt: sama5d4ek: Add support of QT1070 and Maxtouch

As the EK board comes with a PDA 7" screen, add the touch buttons
and touchscreen for it.

Signed-off-by: Patrice Vilchez <patrice.vilchez@atmel.com>
[nicolas.ferre@atmel.com: add commit message]
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>