Staging: batman-adv: Make hash_iterate inlineable

hash_iterate is next to the function pointers the most called function
related to hashes which benefits from inlining as it is uses in loops.

Reported-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sven Eckelmann <sven.eckelmann@gmx.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>