xfs: use xfs_defer_create_done for the relogging operation

Now that we have a helper to handle creating a log intent done item and
updating all the necessary state flags, use it to reduce boilerplate in
the ->iop_relog implementations.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>