ARM: dts: imx6ull-colibri: add touchscreen device nodes

Move all Atmel nodes from the board-level into the main module-level
device tree and prepare the device trees for use with Atmel MXT device
tree overlays. Also, add required pinmux groups.

The common scheme for pin groups in touch screen overlays is as follows:
- pinctrl_atmel_conn - SODIMM 106/107 pins for INT/RST signals (default)
- pinctrl_atmel_adap - SODIMM   28/30 pins for INT/RST signals.

Signed-off-by: Denys Drozdov <denys.drozdov@toradex.com>
Signed-off-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>