netfilter: add nf_conntrack_netbios_ns to kmod-nf-nathelper-extra

netfilter: add nf_conntrack_netbios_ns to kmod-nf-nathelper-extra

NetBIOS name service requests are sent as broadcast messages from an
unprivileged port and responded to with unicast messages to the
same port. This make them hard to firewall properly because connection
tracking doesn't deal with broadcasts.

So let´s enable this in the kernel and add them to 'kmod-nf-nathelper-extra'.

Signed-off-by: Florian Eckert <fe@dev.tdt.de>