md: centralize ->array_sectors modifications

Get personalities out of the business of directly modifying
->array_sectors.  Lays groundwork to introduce policy on when
->array_sectors can be modified.

Reviewed-by: Andre Noll <maan@systemlinux.org>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index a2a83b0..044116b 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -2059,7 +2059,7 @@
 	/*
 	 * Ok, everything is just fine now
 	 */
-	mddev->array_sectors = raid1_size(mddev, 0, 0);
+	md_set_array_sectors(mddev, raid1_size(mddev, 0, 0));
 
 	mddev->queue->unplug_fn = raid1_unplug;
 	mddev->queue->backing_dev_info.congested_fn = raid1_congested;
@@ -2124,7 +2124,7 @@
 	 * any io in the removed space completes, but it hardly seems
 	 * worth it.
 	 */
-	mddev->array_sectors = raid1_size(mddev, sectors, 0);
+	md_set_array_sectors(mddev, raid1_size(mddev, sectors, 0));
 	set_capacity(mddev->gendisk, mddev->array_sectors);
 	mddev->changed = 1;
 	if (mddev->array_sectors > mddev->dev_sectors &&