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>

drivers/md/dm.c

@@ -37,8 +37,8 @@ static DEFINE_SPINLOCK(_minor_lock);
 struct dm_io {
 	struct mapped_device *md;
 	int error;
-	struct bio *bio;
 	atomic_t io_count;
+	struct bio *bio;
 	unsigned long start_time;
 };