cpufreq: frequency regulation based on screen on/off events
Cap the max cpu frequency to [min .. max/2] when the screen is off, and
to [max/2 .. max] when the screen is off.

If the cpu doesn't support exactly max/2 an appropriate frequency is
chosen, as close as possible to the theoretical value.

Signed-off-by: Andrea Righi <andrea@betterlinux.com>
cpu idle related changes, linux 3.0.84 - > 3.0.85