dm io: remove struct padding

Rearrange struct dm_io.
Shrinks size from 40 -> 32 allowing more objects/slab.

Signed-off-by: Richard Kennedy <richard@rsk.demon.co.uk>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 372369b..efe9690 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -37,8 +37,8 @@
 struct dm_io {
 	struct mapped_device *md;
 	int error;
-	struct bio *bio;
 	atomic_t io_count;
+	struct bio *bio;
 	unsigned long start_time;
 };