agp: kill agp_flush_chipset and corresponding ioctl

The intel drm calls the chipset functions now directly. Userspace
never called the corresponding ioctl, hence it can be killed, too.

Cc: Dave Airlie <airlied@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

drivers/char/agp/agp.h

@@ -120,7 +120,6 @@ struct agp_bridge_driver {
 	void (*agp_destroy_page)(struct page *, int flags);
 	void (*agp_destroy_pages)(struct agp_memory *);
 	int (*agp_type_to_mask_type) (struct agp_bridge_data *, int);
-	void (*chipset_flush)(struct agp_bridge_data *);
 };
 
 struct agp_bridge_data {