omnia: get eth interface name from label instead of port id

Read of_node/label instead of phys_switch_id and don't try to get port label from "LAN" + port_id.

Change labels on Mox from 0..n-1 to LAN1..LANn. E.g.: LAN1 to LAN12

Output on Omnia should remain the same (i.e. LAN0..LAN4).