exofs: Fix "add bdi backing to mount session" fall out

The patch: add bdi backing to mount session
	(b3d0ab7e)

Has a bug in the placement of the bdi member at
struct exofs_sb_info. The layout member must be kept
last.
Signed-off-by: NBoaz Harrosh <bharrosh@panasas.com>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

fs/exofs/exofs.h

@@ -85,6 +85,7 @@ struct exofs_sb_info {
 	u32		s_next_generation;	/* next gen # to use          */
 	atomic_t	s_curr_pending;		/* number of pending commands */
 	uint8_t		s_cred[OSD_CAP_LEN];	/* credential for the fscb    */
+	struct 		backing_dev_info bdi;	/* register our bdi with VFS  */
 
 	struct pnfs_osd_data_map data_map;	/* Default raid to use
 						 * FIXME: Needed ?
@@ -93,7 +94,6 @@ struct exofs_sb_info {
 	struct exofs_layout	layout;		/* Default files layout,
 						 * contains the variable osd_dev
 						 * array. Keep last */
-	struct backing_dev_info bdi;
 	struct osd_dev	*_min_one_dev[1];	/* Place holder for one dev   */
 };