mvebu: add Methode euroDPU support
Add support for Methode euroDPU which is based on uDPU but does not
have a second SFP cage, instead of which a Maxlinear G.hn IC is used.
PHY mode is set to 1000Base-X despite Maxlinear IC being capable of
2500Base-X since until 5.15 support for mvebu is available trying to use
2500Base-X will cause buffer overruns for which the fix is not easily
backportable.
Installation instructions:
1. Boot the FIT initramfs image (openwrt-mvebu-cortexa53-methode_edpu-initramfs.itb)
2. sysupgrade using the openwrt-mvebu-cortexa53-methode_edpu-firmware.tgz
Signed-off-by: Robert Marko <robert.marko@sartura.hr>