null_blk: remove duplicate 0 initialization

In function null_add_dev() struct nullb *nullb member is allocated
using kzalloc_node() which returns 0red memory.

In function setup_queues() which is called from the null_add_dev(), on
successful queue allocation we set the nullb->nr_queues = 0 which is not
needed due to earlier use of kzalloc_node().
Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/block/null_blk_main.c

@@ -1489,7 +1489,6 @@ static int setup_queues(struct nullb *nullb)
 	if (!nullb->queues)
 		return -ENOMEM;
 
-	nullb->nr_queues = 0;
 	nullb->queue_depth = nullb->dev->hw_queue_depth;
 
 	return 0;