Staging: batman-adv: Use printk(%pM) for MAC addresses

printk() since kernel version 2.6.29 has supported printing MAC
addresses directly, as an extension to the %p processing. This patch
makes use of this for printk() and bat_dbg(). This will remove the
overhead of using addr_to_string() which is normally never actually
output.

Fixed a typo found by Gus Wirth.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Simon Wunderlich <siwu@hrz.tu-chemnitz.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>