batman-adv: Initialize lockdep class keys for hashes

Different hashes have the same class key because they get
initialised with the same one. For this reason lockdep can create
false warning when they are used recursively.

Re-initialise the key for each hash after the invocation to hash_new()
to avoid this problem.

Signed-off-by: Antonio Quartulli <ordex@autistici.org>
Tested-by: Linus Lüssing <linus.luessing@web.de>
Signed-off-by: Marek Lindner <lindner_marek@yahoo.de>