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>
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 23c67e0..7c8c01b 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -4440,7 +4440,7 @@
 
 	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);