arm64: dts: colibri-imx8x: Add atmel pinctrl groups

Add pinctrl groups for enabling atmel touchscreen support.
Remove the pads out of pinctrl_hog0 as they now can be enabled more
specific using pinctrl_atmel_conn label.

Signed-off-by: Philippe Schenker <philippe.schenker@toradex.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>