v2: Fix for GPU/CPU thrashing in DMPS off state

[Ilija Hadzic]

The following is the revised patch set that fixes the problem
described in

http://lists.x.org/archives/xorg-driver-ati/2012-December/024027.html

First two patches are unchanged from the first series (sent yesterday),
and are included for completeness sake. The third patch is new and is
another function-neutral prep-patch. The fourth patch implements the
fix and (to the best of my understanding) addresses the comments
received after the first series.

thanks,

Ilija