arm64: dts: Add support for Emtop SoM & Baseboard

Add device tree support for the i.MX8MM Based Emtop SOM-IMX8MMLPD4 (V1)
and IMX8M Mini Baseboard (V1).
Currently supported are serial console, eMMC.

Signed-off-by: Himanshu Bhavani <himanshu.bhavani@siliconsignals.io>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>