the two lonely ring_buffer helper functions are used by the
bat_iv_ogm module only and therefore they can be moved
inside it.
Reported-by: NMarek Lindner <lindner_marek@yahoo.de>
Signed-off-by: NAntonio Quartulli <ordex@autistici.org>
Signed-off-by: NMarek Lindner <lindner_marek@yahoo.de>