ramips: fix first boot network configuration for TOZED ZLT S12 PRO

ramips: fix first boot network configuration for TOZED ZLT S12 PRO

The network configuration at first boot for TOZED ZLT S12 PRO lacks setting
up the LAN and WAN network interfaces. Address this. The WAN port is
advertised as WAN/LAN on the device and is put on LAN on stock firmware so
put it on LAN here as well.

Fixes: ce1f9fa625 ("ramips: add support for TOZED ZLT S12 PRO")
Reported-by: Andre Cruz <me@1conan.com>
Signed-off-by: Arınç ÜNAL <arinc.unal@arinc9.com>
(cherry picked from commit b61253f92abb4c0d21ec7358a74438eae8d7e6b4)