[LEDE-DEV] ar71xx: swconfig does not reflect changes

[milani at betternet.co]

I own an ar71xx bboard (GL-6416 to be exact). Whether the ethernet cable 
is connected to WAN port or not, running `swconfig dev switch0 show` 
returns the following:

```
Global attributes:
	enable_vlan: 0
Port 0:
	pvid: 0
	link: port:0 link:up speed:1000baseT full-duplex txflow rxflow
Port 1:
	pvid: 0
	link: port:1 link:down
Port 2:
	pvid: 0
	link: port:2 link:down
Port 3:
	pvid: 0
	link: port:3 link:down
Port 4:
	pvid: 0
	link: port:4 link:down
VLAN 0:
	vid: 0
	ports: 0 1 2 3 4
```

But if I connect the cable to the LAN port, the result is:

```
Global attributes:
	enable_vlan: 0
Port 0:
	pvid: 0
	link: port:0 link:up speed:1000baseT full-duplex txflow rxflow
Port 1:
	pvid: 0
	link: port:1 link:up speed:100baseT full-duplex auto
Port 2:
	pvid: 0
	link: port:2 link:down
Port 3:
	pvid: 0
	link: port:3 link:down
Port 4:
	pvid: 0
	link: port:4 link:down
VLAN 0:
	vid: 0
	ports: 0 1 2 3 4
```

Is it usual behavior? I suppose not, since my other router (mt762a) 
works as expected, that is it reflects the changes for the WAN port.