webrepl: Support LAN as well as WLAN boards.

[jimmo]

When webrepl starts, it prints out the IP address to stdout, however it does this by querying the network.WLAN object -- https://.com/micropython/micropython-lib/blob/master/micropython/net/webrepl/webrepl.py#L105

This should also try network.LAN (and not fail if network.LAN xor network.WLAN are unavailable).