This reverts commit d025e9e2.

This causes corruption for a number of users and needs further
investigation in the next cycle.
https://bugzilla.kernel.org/show_bug.cgi?id=52491
https://bugs.freedesktop.org/show_bug.cgi?id=58659
http://lists.freedesktop.org/archives/dri-devel/2013-January/032961.htmlSigned-off-by: NAlex Deucher <alexander.deucher@amd.com>