nvme: remove nvm_ndev from ns

Now that the lightnvm driver is removed, we don't need a pointer to it's
now non-existent struct.

Signed-off-by: Keith Busch <kbusch@kernel.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>

drivers/nvme/host/nvme.h

@@ -444,7 +444,6 @@ struct nvme_ns {
 	u32 ana_grpid;
 #endif
 	struct list_head siblings;
-	struct nvm_dev *ndev;
 	struct kref kref;
 	struct nvme_ns_head *head;