arm/dt: 8974-liquid: Add Atmel touchscreen device

Add Atmel touch-screen device to liquid device tree.
This includes configuration data for Atmel controller,
which configures power settings, number of touchses supported,
resolution and much more.

CRs-Fixed: 360517
Change-Id: I85958061298b7ebca1ff375386346bafb45ccbcf
Signed-off-by: Amir Samuelov <amirs@codeaurora.org>
Signed-off-by: Amy Maloche <amaloche@codeaurora.org>