Staging: batman-adv: Replace KERN_DEBUG with bat_dbg

Ameya Palande requested we replace printk(KERN_DEBUG "") by pr_debug()
I decided it was better to use our debug macro.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Acked-by: Marek Lindner <lindner_marek@yahoo.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>