dm: convert to bioset_init()/mempool_init()

Convert dm to embedded bio sets.

Acked-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/drivers/md/dm-core.h b/drivers/md/dm-core.h
index 3222e21..f21c5d2 100644
--- a/drivers/md/dm-core.h
+++ b/drivers/md/dm-core.h
@@ -91,8 +91,8 @@ struct mapped_device {
 	/*
 	 * io objects are allocated from here.
 	 */
-	struct bio_set *io_bs;
-	struct bio_set *bs;
+	struct bio_set io_bs;
+	struct bio_set bs;
 
 	/*
 	 * freeze/thaw support require holding onto a super block