Handle devices with wan_dev network section

[lantis1008]

@obsy can you please check this solution.
Reference:

Add to list: on some platform default mac addresses extracted from eeprom are stored in wan_dev/lan_dev section, not wan/lan itself. "Use Custom MAC Address:" should set mac in wan_dev section (if exists).

network.lan=interface
network.lan.type='bridge'
network.lan.ifname='eth0.1'
network.lan.proto='static'
network.lan.ipaddr='192.168.1.1'
network.lan.netmask='255.255.255.0'
network.lan.ip6assign='60'
network.lan_dev=device
network.lan_dev.name='eth0.1'
network.lan_dev.macaddr='d4:6e:0e:d0:49:68'
network.wan_dev=device
network.wan_dev.name='eth0.2'
network.wan_dev.macaddr='d4:6e:0e:d0:49:69'

Couple of things i'm not sure on, and would be good if you could test/confirm:

1. Is it necessary to delete wan_dev sections if we delete the main wan section. E.g. lines 154 and 160 (and others). If the wan_dev section causes no issues when it is present, then we will leave it. Definitely concerned about the implications when using wireless or usb protocols for wan
2. I think gargoyle_header_footer also needs updating (line 945) although it will usually work without it anyway as the mac is sourced directly from the interface. But would be good to add as an extra check. Can you please confirm it works ok as it is, and your opinion on whether it should be modified (i think yes)?
3. I've done nothing with lan_dev. Do you foresee anytime we need to do this?

[obsy]

1. no. The wan_dev section can remain even if wan does not exist or wan is qmi proto.
2. check later.

[obsy]

Looks good.

Initial settings

root@Gargoyle:~# ifconfig eth0.2; uci show network.wan; uci show network.wan_dev
eth0.2    Link encap:Ethernet  HWaddr D4:6E:0E:D0:49:69  
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:24 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:0 (0.0 B)  TX bytes:6280 (6.1 KiB)

network.wan=interface
network.wan.ifname='eth0.2'
network.wan.proto='dhcp'
network.wan_dev=device
network.wan_dev.name='eth0.2'
network.wan_dev.macaddr='d4:6e:0e:d0:49:69'

Set to d4:6e:0e:fe:fe:fe, without patch:

eth0.2    Link encap:Ethernet  HWaddr D4:6E:0E:D0:49:69  
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:9 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:0 (0.0 B)  TX bytes:1150 (1.1 KiB)

network.wan=interface
network.wan.ifname='eth0.2'
network.wan.proto='dhcp'
network.wan.macaddr='d4:6e:0e:fe:fe:fe'
network.wan.ipv6='0'
network.wan_dev=device
network.wan_dev.name='eth0.2'
network.wan_dev.macaddr='d4:6e:0e:d0:49:69'

after patch & set to d4:6e:0e:fe:fe:fe

root@Gargoyle:~# ifconfig eth0.2; uci show network.wan; uci show network.wan_dev
eth0.2    Link encap:Ethernet  HWaddr D4:6E:0E:FE:FE:FE  
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:21 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:0 (0.0 B)  TX bytes:5254 (5.1 KiB)

network.wan=interface
network.wan.ifname='eth0.2'
network.wan.proto='dhcp'
network.wan.ipv6='0'
network.wan_dev=device
network.wan_dev.name='eth0.2'
network.wan_dev.macaddr='d4:6e:0e:fe:fe:fe'