arm64: mvebu: Add basic support for uDPU board

arm64: mvebu: Add basic support for uDPU board

This adds initial support for micro-DPU (uDPU) board which is based on Armada-3720 SoC.
micro-DPU is the single-port FTTdp "distribution point unit" made by Methode Electronics
which offers complete modularity with replaceable SFP modules both for uplink and downlink
(G.hn over twisted-pair, G.hn over coax, 1G and 2.5G Ethernet over Cat-5e cable).

On-board features:
- 512 MiB DDR3
- 2 x 2.5G SFP via HSGMII SERDES interface to the A3720 SoC
- USB 2.0 Type-C connector
- 4GB eMMC
- ETSI TS 101548 reverse powering via twisted pair (RJ45) or coax (F Type)

Cc: Luka Perkov <luka.perkov@sartura.hr>
Cc: Luis Torres <luis.torres@methode.com>
Cc: Scott Roberts <scott.roberts@telus.com>
Cc: Paul Arola <paul.arola@telus.com>
Signed-off-by: Vladimir Vid <vladimir.vid@sartura.hr>
Reviewed-by: Stefan Roese <sr@denx.de>
Signed-off-by: Stefan Roese <sr@denx.de>