When the TVLV parsing routine succeed the skb is left
untouched thus leading to a memory leak.

Fix this by consuming the skb in case of success.

Introduced by ef261577
("batman-adv: tvlv - basic infrastructure")
Reported-by: NRussel Senior <russell@personaltelco.net>
Signed-off-by: NAntonio Quartulli <antonio@open-mesh.com>
Tested-by: NRussell Senior <russell@personaltelco.net>
Signed-off-by: NMarek Lindner <mareklindner@neomailbox.ch>