nvme-auth: uninitialized variable in nvme_auth_transform_key()

A couple of the early error gotos call kfree_sensitive(transformed_key);
before "transformed_key" has been initialized.

Fixes: db1312dd ("nvmet: implement basic In-Band Authentication")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>