ARM: dts: imx6ul-pico-hobbit: Move SoM related part to imx6ul-pico.dtsi

imx6ul-pico-hobbit board contains:

- One SoM board (imx6ul pico)
- One base board (hobbit).

In order to make it easier for adding support for other board variants,
move the commom SoM part to the imx6ul-pico.dtsi file.
Signed-off-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>