dm raid: remove unnecessary discard limits for raid0 and raid10

Commit 29efc39 ("md/md0: optimize raid0 discard handling") and
commit d30588b ("md/raid10: improve raid10 discard request")
remove MD raid0's and raid10's inability to properly handle large
discards. So eliminate associated constraints from dm-raid's support.

Depends-on: 29efc39 ("md/md0: optimize raid0 discard handling")
Depends-on: d30588b ("md/raid10: improve raid10 discard request")
Reported-by: Matthew Ruffell <matthew.ruffell@canonical.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

drivers/md/dm-raid.c

@@ -3750,15 +3750,6 @@ static void raid_io_hints(struct dm_target *ti, struct queue_limits *limits)
 
 	blk_limits_io_min(limits, chunk_size_bytes);
 	blk_limits_io_opt(limits, chunk_size_bytes * mddev_data_stripes(rs));
-
-	/*
-	 * RAID0 and RAID10 personalities require bio splitting,
-	 * RAID1/4/5/6 don't and process large discard bios properly.
-	 */
-	if (rs_is_raid0(rs) || rs_is_raid10(rs)) {
-		limits->discard_granularity = chunk_size_bytes;
-		limits->max_discard_sectors = rs->md.chunk_sectors;
-	}
 }
 
 static void raid_postsuspend(struct dm_target *ti)