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>