batman-adv: format multi-line if in the correct way

in an multi-line if statement leading edges should line up to the opening
parenthesis

Reported-by: David Miller <davem@davemloft.net>
Signed-off-by: Antonio Quartulli <ordex@autistici.org>
Signed-off-by: Marek Lindner <lindner_marek@yahoo.de>