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_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index d1b7dec..354b00f 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -747,7 +747,7 @@
 	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.