ARM: dts: imx7d-pico: Add the imx7d-pico-hobbit variant

The imx7d-pico-hobbit contains a imx7d-pico SoM and a hobbit baseboard.

Add support for it.

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>