xfs: add a flag to release log items on commit

We have various items that are released from ->iop_comitting.  Add a
flag to just call ->iop_release from the commit path to avoid tons
of boilerplate code.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>