block: move the ->devnode callback to struct block_device_operations

There really isn't any good reason to stash a method directly into
struct gendisk.  Move it together with the other block device
operations.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

include/linux/blkdev.h

@@ -1697,6 +1697,7 @@ struct block_device_operations {
 	void (*swap_slot_free_notify) (struct block_device *, unsigned long);
 	int (*report_zones)(struct gendisk *, sector_t sector,
 			unsigned int nr_zones, report_zones_cb cb, void *data);
+	char *(*devnode)(struct gendisk *disk, umode_t *mode);
 	struct module *owner;
 	const struct pr_ops *pr_ops;
 };

include/linux/genhd.h

@@ -191,7 +191,6 @@ struct gendisk {
                                          * disks that can't be partitioned. */
 
 	char disk_name[DISK_NAME_LEN];	/* name of major driver */
-	char *(*devnode)(struct gendisk *gd, umode_t *mode);
 
 	unsigned short events;		/* supported events */
 	unsigned short event_flags;	/* flags related to event processing */