When the MAC address of the primary interface is changed,
update the originator address in the ELP and OGM skb buffers as
well in order to reflect the change.

Fixes: d6f94d91 ("batman-adv: ELP - adding basic infrastructure")
Reported-by: Marek Lindner <marek@neomailbox.ch>
Signed-off-by: Antonio Quartulli <a@unstable.cc>