drm: Remove the minor master list

It doesn't appear to be used anywhere.

Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: David Herrmann <dh.herrmann@gmail.com>

include/drm/drmP.h

@@ -689,7 +689,6 @@ struct drm_master {
 
 	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 */
@@ -1022,7 +1021,6 @@ struct drm_minor {
 	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;
 };