Staging: batman-adv: Wrapper functions for sysfs storing

Sysfs configuration options that just took a boolean value
(enable(d)/disable(d)/0/1) and integer setting basically all had the same
structure.

To avoid even more copy and pasting in the future and to make introducing
new configuration parameters for batman-adv simpler, more generic
wrapper functions are being introduced with this commit. They can deal with
boolean and unsigned integer parameters, storing them in the specified
atomic_t variables.
Signed-off-by: Linus Lüssing <linus.luessing@web.de>
Signed-off-by: Sven Eckelmann <sven.eckelmann@gmx.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>