cpufreq: add generic get_cpuidle_time to the cpufreq headers so that we don't need to implement this everytime we need it.

Signed-off-by: Francisco Franco <franciscofranco.1990@gmail.com>

Conflicts:
	drivers/cpufreq/cpufreq.c

michael1900: fix a cherry-ppick error
cpufreq: remove get_cpuidle_time from governors and fix them