statistics-defaults: drop dependency to olsr

[SvenRoederer]

the package "freifunk-berlin-statistics-defaults" depends on olsr, via olsrd-mod-txtinfo. As the package only setup up some uci parameters this is not a dependency to the binary.
On our way to change the routing-protocol of the net, this dependency needs to be removed.

Even it's not known to which protocol we will go to, removing OLSR is a first step required anyway.

[SvenRoederer]

When we discussed on #776, where was also a short sidenote on "getting rid of olsrv1", as this will remove SmartGateway problems also.

Probably the dependency of the Makefile can be removed straight away, when Luci takes care of not enabling the olsr-plugin of collectd when it's not installed (https://github.com/freifunk-berlin/firmware-packages/blob/fd19100f5fa56635889cb78109dbc4a555f79d99/defaults/freifunk-berlin-statistics-defaults/uci-defaults/freifunk-berlin-statistics-defaults#L61)