cpuidle: Add decaying history logic to menu idle predictor

cpuidle: Add decaying history logic to menu idle predictor

this patch is ported from linux upstream git commit
816bb611e41be29b476dc16f6297eb551bf4d747

the original description is:
"
Add decaying history of predicted idle time, instead of using the last
early wakeup. This logic helps menu governor do better job of
predicting idle time.

With this change, we also measured noticable (~8%) power savings on a
DP server system with CPUs supporting deep C states, when system was
lightly loaded. There was no change to power or perf on other load
conditions.

Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>
"

In Xen environment, we also observe this patch reduce the idle power
fluctuation.  In one DP server, when system is purely idle, the watts
stdev/average reduce from 6% to 2%. it is helpful for idle power
measurement accuracy.  There is no performance and power change when
system is loaded.

Signed-off-by: Yu Ke <ke.yu@intel.com>