md/raid1:Remove unnecessary rcu_dereference(conf->mirrors[i].rdev).

Because rde->nr_pending > 0,so can not remove this disk.
And in any case, we aren't holding rcu_read_lock()
Signed-off-by: majianpeng <majianpeng@gmail.com>
Signed-off-by: NeilBrown <neilb@suse.de>

drivers/md/raid1.c

@@ -2386,8 +2386,7 @@ static sector_t sync_request(struct mddev *mddev, sector_t sector_nr, int *skipp
 		int ok = 1;
 		for (i = 0 ; i < conf->raid_disks * 2 ; i++)
 			if (r1_bio->bios[i]->bi_end_io == end_sync_write) {
-				struct md_rdev *rdev =
-					rcu_dereference(conf->mirrors[i].rdev);
+				struct md_rdev *rdev = conf->mirrors[i].rdev;
 				ok = rdev_set_badblocks(rdev, sector_nr,
 							min_bad, 0
 					) && ok;