v3: Fix for GPU/CPU thrashing in DPMS off state

[Ilija Hadzic]

The following patch series is the version 3 of the fix that prevents
the application from rendering at uncontrolled rate as explained
in this thread:

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

In this series all attempts to be "smart" and emulate the real
CRTC behavior have been thrown away. Instead, when CRTC is disabled
we just defer the swaps by a hard-coded constant, with the sole
objective to prevent unecessary power dissipation. As I proposed
here:

http://lists.x.org/archives/xorg-driver-ati/2012-December/024193.html

the more "sophisticated" fix will be provided later in a set of follow-on
patches.

thanks,

Ilija