dm: fix the second dec_pending() argument in __split_and_process_bio()

Detected by sparse.

Fixes: 4e4cbee ("block: switch bios to blk_status_t")
Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Tested-by: Laurence Oberman <loberman@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

drivers/md/dm.c

@@ -1523,7 +1523,7 @@ static void __split_and_process_bio(struct mapped_device *md,
 	}
 
 	/* drop the extra reference count */
-	dec_pending(ci.io, error);
+	dec_pending(ci.io, errno_to_blk_status(error));
 }
 /*-----------------------------------------------------------------
  * CRUD END