batman-adv: Prefix bitarray non-static functions with batadv_

batman-adv: Prefix bitarray non-static functions with batadv_

batman-adv can be compiled as part of the kernel instead of an module. In that
case the linker will see all non-static symbols of batman-adv and all other
non-static symbols of the kernel. This could lead to symbol collisions. A
prefix for the batman-adv symbols that defines their private namespace avoids
such a problem.

Reported-by: David Miller <[email protected]>
Signed-off-by: Sven Eckelmann <[email protected]>