drm/i915: Correct obj->mm_list link to dev_priv->dev_priv->mm.inactive_list

obj->mm_list link to dev_priv->mm.inactive_list/active_list
obj->global_list link to dev_priv->mm.unbound_list/bound_list

This regression has been introduced in

commit 93927ca5
Author: Daniel Vetter <daniel.vetter@ffwll.ch>
Date:   Thu Jan 10 18:03:00 2013 +0100

    drm/i915: Revert shrinker changes from "Track unbound pages"

Cc: stable@vger.kernel.org
Signed-off-by: Xiong Zhang <xiong.y.zhang@intel.com>
[danvet: Add regression notice.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_gem.c

@@ -4623,7 +4623,7 @@ i915_gem_inactive_shrink(struct shrinker *shrinker, struct shrink_control *sc)
 	list_for_each_entry(obj, &dev_priv->mm.unbound_list, global_list)
 		if (obj->pages_pin_count == 0)
 			cnt += obj->base.size >> PAGE_SHIFT;
-	list_for_each_entry(obj, &dev_priv->mm.inactive_list, global_list)
+	list_for_each_entry(obj, &dev_priv->mm.inactive_list, mm_list)
 		if (obj->pin_count == 0 && obj->pages_pin_count == 0)
 			cnt += obj->base.size >> PAGE_SHIFT;