xfs: clean out superfluous dfops dop params/vars

The dfops code still passes around the xfs_defer_ops pointer
superfluously in a few places. Clean this up wherever the
transaction will suffice.

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