blk-wbt: open code wbt_queue_depth_changed in wbt_init

wbt_queue_depth_changed just updates a field and calls another function.
Open code it in wbt_init, so that the local queue variable can be used
instead of the one stored in the rq_qos.  This will allow delaying that
rq_qos->queue assignment in a subsequent patch.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Andreas Herrmann <aherrmann@suse.de>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20230203150400.3199230-12-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-wbt.c

@@ -941,8 +941,8 @@ int wbt_init(struct gendisk *disk)
 	rwb->wc = test_bit(QUEUE_FLAG_WC, &q->queue_flags);
 	rwb->rq_depth.default_depth = RWB_DEF_DEPTH;
 	rwb->min_lat_nsec = wbt_default_latency_nsec(q);
-
-	wbt_queue_depth_changed(&rwb->rqos);
+	rwb->rq_depth.queue_depth = blk_queue_depth(q);
+	wbt_update_limits(rwb);
 
 	/*
 	 * Assign rwb and add the stats callback.