batman-adv: Remove the repeated declaration

Function 'batadv_bla_claim_dump' is declared twice, so remove the
repeated declaration.

Signed-off-by: Shaokun Zhang <zhangshaokun@hisilicon.com>
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>