luci-mod-freifunk: eliminate use of luci.sys.net.deviceinfo()

The result of the luci.sys.net.deviceinfo() call was never actually used
anywhere in the following code, so simply drop the invocation.

Signed-off-by: Jo-Philipp Wich <jo@mein.io>

modules/luci-mod-freifunk/luasrc/controller/freifunk/freifunk.lua

@@ -188,7 +188,6 @@ function jsonstatus()
 	root.network = {}
 	root.wireless = {devices = {}, interfaces = {}, status = {}}
 	local wifs = root.wireless.interfaces
-	local netdata = luci.sys.net.deviceinfo() or {}
 
 	for _, vif in ipairs(ffwifs) do
 		root.network[vif] = cursor:get_all("network", vif)