Revert "staging: batman-adv: Use linux/etherdevice.h address helper functions"

This reverts commit 5712dc7fc812d1bdbc5e634d389bc759d4e7550c.

Turns out the batman maintainers didn't like the implementation of it,
and the original author was going to rework it to meet their approval,
and I applied it without fully realizing all of this.

My fault.

Cc: Marek Lindner <lindner_marek@yahoo.de>
Cc: Simon Wunderlich <siwu@hrz.tu-chemnitz.de>
Cc: Andrew Lunn <andrew@lunn.ch>
Cc: Tobias Klauser <tklauser@distanz.ch>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>