[RFC] Octeon: EdgeRouter Lite fixes

[Stijn Segers]

These patches align the EdgeRouter Lite device with modern OpenWrt
practices:
- Use vendor prefix for board_name: ubnt,erlite instead of erlite.
- Set the model to "Ubiquiti EdgeRouter Lite".
- Add an EdgeRouter Lite match in /etc/board.d/01_network so all
  network interfaces get configured: eth0 as WAN, eth1 and eth2 as a LAN
  bridge. This is similar to what is done for the PC Engines APU line
  and for the Ubiquiti EdgeRouter 4 (also octeon).

I've made this an RFC because of the hackish way I set the model,
but I think this is the cleanest way to do it (short of overwriting the
machine variable altogether). Also, lots of Ubiquiti devices seem to use
shortened codenames in board_name, but recent addition EdgeRouter 4 e.g.
does not, so I'm not sure what's best practice here. It doesn't look
like the codenames are needed for anything?

This will of course break sysupgrade, but since the default network
layout changes, I'm not sure if we want to keep compatibility?

Thanks

Stijn