With commit 38f25255 ("block: add __blkdev_issue_discard") DM thinp
no longer needs to carry its own async discard method.
Signed-off-by: NMike Snitzer <snitzer@redhat.com>
Acked-by: NJoe Thornber <ejt@redhat.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>