null_blk: Do not set disk->nr_zones

In null_register_zoned_dev(), there is no need to set disk->nr_zones as
the now uncoditional call to blk_revalidate_disk_zones() will do that.
So remove the assignment using bdev_nr_zones().

Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Link: https://lore.kernel.org/r/20240621031506.759397-2-dlemoal@kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: damien-lemoal

drivers/block/null_blk/zoned.c

@@ -171,8 +171,6 @@ int null_register_zoned_dev(struct nullb *nullb)
 	struct request_queue *q = nullb->q;
 	struct gendisk *disk = nullb->disk;
 
-	disk->nr_zones = bdev_nr_zones(disk->part0);
-
 	pr_info("%s: using %s zone append\n",
 		disk->disk_name,
 		queue_emulates_zone_append(q) ? "emulated" : "native");