dm: optimize reorder structure

This reorder actually improves performance by 20% (from 39.1s to 32.8s)
on x86-64 quad core Opteron.

I have no explanation for this, possibly it makes some other entries are
better cache-aligned.

Signed-off-by: Mikulas Patocka <[e-mail]>
Signed-off-by: Alasdair G Kergon <[e-mail]>

drivers/md/dm.c

···
 	atomic_t holders;
 	atomic_t open_count;
 
+	/*
+	 * The current mapping.
+	 * Use dm_get_live_table{_fast} or take suspend_lock for
+	 * dereference.
+	 */
+	struct dm_table *map;
+
 	unsigned long flags;
 
 	struct request_queue *queue;
···
 	 * Processing queue (flush)
 	 */
 	struct workqueue_struct *wq;
-
-	/*
-	 * The current mapping.
-	 * Use dm_get_live_table{_fast} or take suspend_lock for
-	 * dereference.
-	 */
-	struct dm_table *map;
 
 	/*
 	 * io objects are allocated from here.