arm64: dts: imx8mp: Add support for DH electronics i.MX8M Plus DHCOM and PDK3

Add support for DH electronics i.MX8M Plus DHCOM SoM on PDK3 carrier board.
Currently supported are serial console, EQoS and FEC ethernets, eMMC, SD,
SPI NOR, CAN, M.2 E-Key or M.2 M-Key PCIe, USB .

Signed-off-by: Marek Vasut <marex@denx.de>
Reviewed-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>