x86: base-files add support for Sophos 135r3/135r3w
The Sophos SG/XG-135 revision 3 has odd numbering of eth ports
where the WAN port (as marked on the case) is:
`eth6` and `eth0`, `eth1`, `eth2`, `eth3`, `eth5`, `eth7`, `eth8` are LAN ports.
Port `eth4` seems to be the SFP port.
Also add the missing LED definition for supported Sophos devices.
Original discussion at:
https://forum.openwrt.org/t/openwrt-on-revision-3-of-sophos-desktop-appliances/152912
Signed-off-by: Stan Grishin <stangri@melmac.ca>