Staging: batman-adv: Remove unneeded rcu_read_lock

Regions which do not use rcu functions don't need to protected by
rcu_read_lock. If we want to protect data from being freed than it must
be covered by the same read-side critical section or otherwise the grace
period may already ended and freed the memory before we called
rcu_read_lock again.

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