nvme: replace the GENHD_FL_UP check in nvme_mpath_shutdown_disk

Use the nvme-internal NVME_NSHEAD_DISK_LIVE flag instead of abusing
the block layer state.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20210809064028.1198327-5-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

drivers/nvme/host/multipath.c

@@ -765,7 +765,7 @@ void nvme_mpath_shutdown_disk(struct nvme_ns_head *head)
 	if (!head->disk)
 		return;
 	kblockd_schedule_work(&head->requeue_work);
-	if (head->disk->flags & GENHD_FL_UP) {
+	if (test_bit(NVME_NSHEAD_DISK_LIVE, &head->flags)) {
 		nvme_cdev_del(&head->cdev, &head->cdev_device);
 		del_gendisk(head->disk);
 	}