drm/i915: don't use ->driver_private anymore

Thanks to the to_intel_bo helper, this change is rather trivial.
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/i915/i915_drv.h

@@ -747,7 +747,7 @@ struct drm_i915_gem_object {
 	atomic_t pending_flip;
 };
 
-#define to_intel_bo(x) ((struct drm_i915_gem_object *) (x)->driver_private)
+#define to_intel_bo(x) container_of(x, struct drm_i915_gem_object, base)
 
 /**
  * Request queue structure.

drivers/gpu/drm/i915/i915_gem.c

@@ -4440,7 +4440,7 @@ struct drm_gem_object * i915_gem_alloc_object(struct drm_device *dev,
 
 	obj->agp_type = AGP_USER_MEMORY;
 
-	obj->base.driver_private = obj;
+	obj->base.driver_private = NULL;
 	obj->obj = &obj->base;
 	obj->fence_reg = I915_FENCE_REG_NONE;
 	INIT_LIST_HEAD(&obj->list);