cpufreq: add generic get_cpuidle_time

Easier to maintain this in one place.

Signed-off-by: Blechd0se <alex.christ@hotmail.de>

Conflicts:
	drivers/cpufreq/cpufreq.c
	drivers/cpufreq/cpufreq_conservative.c
	drivers/cpufreq/cpufreq_ondemand.c
drivers: cpufreq: squash in my interactive changes

This commit contains all my changes to the interactive
governor from this branch; https://github.com/Blechd0se/kernel-moto-g/blob/97def5b37f3771996df904fc9de2be8c13e537f3/drivers/cpufreq/cpufreq_interactive.c

Of course its stripped down, since thread migration code
is just useless on a single core device. The touchboost
solution has dependency, in case somebody goes wild and wants
to revert this beauty.

Signed-off-by: Blechd0se <alex.christ@hotmail.de>