Staging: batman-adv: Remove dead max addr and obsolete VIS_FORMAT strings

Max address is not being used anywhere and just misleading, therefore
removing it. VIS_FORMAT string is now obsolete, so also remove it.

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