nvme-loop: reset queue count to 1 in nvme_loop_destroy_io_queues()

The queue count is increased in nvme_loop_init_io_queues(), so we
need to reset it to 1 at the end of nvme_loop_destroy_io_queues().
Otherwise the function is not re-entrant safe, and crash will happen
during concurrent reset and remove calls.

Signed-off-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

drivers/nvme/target/loop.c

@@ -299,6 +299,7 @@ static void nvme_loop_destroy_io_queues(struct nvme_loop_ctrl *ctrl)
 		clear_bit(NVME_LOOP_Q_LIVE, &ctrl->queues[i].flags);
 		nvmet_sq_destroy(&ctrl->queues[i].nvme_sq);
 	}
+	ctrl->ctrl.queue_count = 1;
 }
 
 static int nvme_loop_init_io_queues(struct nvme_loop_ctrl *ctrl)