md/raid5: remove setting of ->queue_lock

We previously needed to set ->queue_lock to match the raid5
device_lock so we could safely use queue_flag_* operations (e.g. for
plugging). which test the ->queue_lock is in fact locked.

However that need has completely gone away and is unlikely to come
back to remove this now-pointless setting.
Signed-off-by: NeilBrown <neilb@suse.de>

drivers/md/raid5.c

@@ -5151,7 +5151,6 @@ static int run(mddev_t *mddev)
 
 		mddev->queue->backing_dev_info.congested_data = mddev;
 		mddev->queue->backing_dev_info.congested_fn = raid5_congested;
-		mddev->queue->queue_lock = &conf->device_lock;
 
 		chunk_size = mddev->chunk_sectors << 9;
 		blk_queue_io_min(mddev->queue, chunk_size);