btrfs: use BLK_STS defines where needed

At few places we could use BLK_STS_OK and BLK_STS_NOSUPP.

Signed-off-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: Satoru Taekeuchi <satoru.takeuchi@gmail.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ dropped first hunk btrfs_endio_direct_read ]
Signed-off-by: David Sterba <dsterba@suse.com>
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 4931b2d..56ed01f 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -6029,7 +6029,7 @@ static void btrfs_end_bio(struct bio *bio)
 			 * this bio is actually up to date, we didn't
 			 * go over the max number of errors
 			 */
-			bio->bi_status = 0;
+			bio->bi_status = BLK_STS_OK;
 		}
 
 		btrfs_end_bbio(bbio, bio);