Staging: batman-adv: Add include guards to all header files

We include different header files indirectly to the same source file.
This creates weird compiler errors from time to time. Include guards
should prefend that functions/variables/... gets redefined by itself.

Signed-off-by: Sven Eckelmann <sven.eckelmann@gmx.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>