dm: remove unused flush target method

Remove unused dm_flush_fn .flush target method from header.

This was left-over from the FLUSH/FUA conversion and is no longer used.
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

include/linux/device-mapper.h

@@ -66,7 +66,6 @@ typedef int (*dm_request_endio_fn) (struct dm_target *ti,
 				    struct request *clone, int error,
 				    union map_info *map_context);
 
-typedef void (*dm_flush_fn) (struct dm_target *ti);
 typedef void (*dm_presuspend_fn) (struct dm_target *ti);
 typedef void (*dm_postsuspend_fn) (struct dm_target *ti);
 typedef int (*dm_preresume_fn) (struct dm_target *ti);
@@ -139,7 +138,6 @@ struct target_type {
 	dm_map_request_fn map_rq;
 	dm_endio_fn end_io;
 	dm_request_endio_fn rq_end_io;
-	dm_flush_fn flush;
 	dm_presuspend_fn presuspend;
 	dm_postsuspend_fn postsuspend;
 	dm_preresume_fn preresume;