Currently the MTU of a babelpeers is not configurable, nor set to a
default value. If present, the `mtu` option is now copied to the
interface section, otherwise it is set to a default value of 1500.
Warning for VLAN Interfaces:
For MTUs larger than 1500 to take effect, the parent interface also
needs adjusting. E.g. setting `eth0.100` to an MTU larger than the MTU
of `eth0` will not work.
At this point, manually add the following section to
`/etc/config/network`:
```
config interface
option ifname 'eth0'
option mtu '1570'
```
Beware that this will cause any child interface of `eth0` to have the
same large MTU.
Signed-off-by: Johannes Kimmel <fff@bareminimum.eu>
Johannes Kimmel