mvebu: fix LAN/WAN port assignment on ClearFog Base/Pro

mvebu: fix LAN/WAN port assignment on ClearFog Base/Pro

The comments in code already describe the intended lan / wan assignment:
lan: switch
wan: standalone ethernet and sfp

Update the interface handles to match the comments, as observed with
OpenWRT-19.07-rc2 on a Clearfog Pro Rev 2.0.

This also matches the effective assignment on master, while the actual
interface names (ethX) are different due to the reassignment in
06_set_iface_mac, which is included in 19.07 but was dropped for master.

Signed-off-by: Josua Mayer <josua.mayer@jm0.eu>
[extend commit message]
Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>