[ffwizard] freifunk-berlin/firmware#124 add interfaces to luci_statistic...

...s
mh... is works for me. it's is also [the same in controller](https://github.com/freifunk-berlin/packages-berlin/blob/master/utils/luci-app-ffwizard-berlin/luasrc/controller/assistent/assistent.lua#L116) (i also had to change that in one of the previous commits)