firewall: don't apply default udp/68 rule to ip6tables

SVN-Revision: 21509

package/firewall/files/firewall.config

@@ -31,6 +31,7 @@ config rule
 	option proto		udp
 	option dest_port	68
 	option target		ACCEPT
+	option family	ipv4
 
 #Allow ping
 config rule