openwrt: get rid of the default router packages

- removes e.g. dnsmasq, firewall
- needs to add some of the basic packages to fff-base

Signed-off-by: Tim Niemeyer <tim@tn-x.org>
Reviewed-by: Christian Dresel <fff@chrisi01.de>
Reviewed-by: Tobias Klaus <tk+ff@meskal.net>