arm: mvebu: add support for Methode eDPU

Methode eDPU is an Armada 3720 power board based on the Methode uDPU.

They feature the same CPU, RAM, and storage as well as the form factor.

However, eDPU only has one SFP slot plus a copper G.hn port which does not
work under U-boot.

In order to reduce duplication, split the uDPU DTS into a common one.

Signed-off-by: Robert Marko <robert.marko@sartura.hr>
Reviewed-by: Stefan Roese <sr@denx.de>