Introduce imx6ull-colibri-u-boot.dtsi for u-boot specific properties to
keep original imx6ull-colibri.dts in sync with Linux.

Move all contents of imx6ull-colibri.dts to imx6ull-colibri.dtsi +
additionally fix checkpatch warnings.
Reviewed-by: NOleksandr Suvorov <oleksandr.suvorov@toradex.com>
Reviewed-by: NFabio Estevam <festevam@gmail.com>
Signed-off-by: NIgor Opaniuk <igor.opaniuk@toradex.com>