For passing authentication keys to the checksumming functions we need a
container for the key.
Pass in a btrfs_fs_info to btrfs_csum_data() so we can use the fs_info
as a container for the authentication key.
Note this is not always possible for all callers of btrfs_csum_data() so
we're just passing in NULL for now
Functions calling btrfs_csum_data() with a NULL fs_info argument are
currently not supported in the context of an authenticated file system.
Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: David Sterba <dsterba@suse.com>
