arm64: dts: imx: Add Beacon i.MX8M Nano development kit

Beacon Embeddedworks is launching a development kit based on the
i.MX8M Nano 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 PDM microphone, and a single USB OTG.

The baseboard is capable of two different, mutually exclusive video
outputs, so the common items are in the baseboard file.  When
the video becomes available, LVDS output will be added to this kit
file, and a second kit file will be added to support HDMI.

Signed-off-by: Adam Ford <aford173@gmail.com>
Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>