arm64: dts: freescale: Introduce imx8mp-beacon-kit

Beacon Embedded has an i.MX8M Plus development kit which consists
of a SOM + baseboard.  The SOM includes Bluetooth, WiFi, QSPI, eMMC,
and one Ethernet PHY. The baseboard includes audio, HDMI, USB-C Dual
Role port, USB Hub with five ports, a PCIe slot, and a second Ethernet
PHY.

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