dm: remove invalid sparse __acquires and __releases annotations

Fixes sparse warnings:
drivers/md/dm.c:508:12: warning: context imbalance in 'dm_prepare_ioctl' - wrong count at exit
drivers/md/dm.c:543:13: warning: context imbalance in 'dm_unprepare_ioctl' - wrong count at exit

Fixes: 971888c4 ("dm: hold DM table for duration of ioctl rather than use blkdev_get")
Cc: stable@vger.kernel.org
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

drivers/md/dm.c

@@ -509,7 +509,6 @@ static int dm_blk_report_zones(struct gendisk *disk, sector_t sector,
 
 static int dm_prepare_ioctl(struct mapped_device *md, int *srcu_idx,
 			    struct block_device **bdev)
-	__acquires(md->io_barrier)
 {
 	struct dm_target *tgt;
 	struct dm_table *map;
@@ -543,7 +542,6 @@ static int dm_prepare_ioctl(struct mapped_device *md, int *srcu_idx,
 }
 
 static void dm_unprepare_ioctl(struct mapped_device *md, int srcu_idx)
-	__releases(md->io_barrier)
 {
 	dm_put_live_table(md, srcu_idx);
 }