arm64: dts: imx: Add Beacon i.MX8m-Mini development kit

Beacon Embeddedworks is launching a development kit based on the
i.MX8M Mini SoC.  The kit consists of a System on Module (SOM)
+ baseboard.  The SOM has the SoC, eMMC, and Ethernet. The baseboard
has an wm8962 audio CODEC, a single USB OTG, and three USB host ports.

Signed-off-by: Adam Ford <aford173@gmail.com>
Reviewed-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>