Staging: batman-adv: Move mailing list address to .org

The official mailing list is run on lists.open-mesh.org and it should be
avoided to sent them to lists.open-mesh.net to reduce the number of
receipents and double posts.

Signed-off-by: Sven Eckelmann <sven.eckelmann@gmx.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>