sparse reports:

fs/xfs/xfs_log_recover.c:2017:24: sparse: cast to restricted __be64

Because I used the wrong structure for the on-disk superblock cast
in 50d5c8d8 ("xfs: check LSN ordering for v5 superblocks during
recovery"). Fix it.

Reported-by: kbuild test robot
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NBen Myers <bpm@sgi.com>