drm: Remove the minor master list

It doesn't appear to be used anywhere.

Signed-off-by: Thomas Hellstrom <[e-mail]>
Reviewed-by: David Herrmann <[e-mail]>

drivers/gpu/drm/drm_stub.c

···
 	INIT_LIST_HEAD(&master->magicfree);
 	master->minor = minor;
 
-	list_add_tail(&master->head, &minor->master_list);
-
 	return master;
 }
 
···
 	struct drm_magic_entry *pt, *next;
 	struct drm_device *dev = master->minor->dev;
 	struct drm_map_list *r_list, *list_temp;
-
-	list_del(&master->head);
 
 	if (dev->driver->master_destroy)
 		dev->driver->master_destroy(dev, master);
···
 
 	minor->type = type;
 	minor->dev = dev;
-	INIT_LIST_HEAD(&minor->master_list);
 
 	*drm_minor_get_slot(dev, type) = minor;
 	return 0;

include/drm/drmP.h

···
 
 	struct kref refcount; /* refcount for this master */
 
-	struct list_head head; /**< each minor contains a list of masters */
 	struct drm_minor *minor; /**< link back to minor we are a master for */
 
 	char *unique;			/**< Unique identifier: e.g., busid */
···
 	struct mutex debugfs_lock; /* Protects debugfs_list. */
 
 	struct drm_master *master; /* currently active master for this node */
-	struct list_head master_list;
 	struct drm_mode_group mode_group;
 };