Imported and adjusted cpufreq get_cpu_idle_time from 3.14 by @Alucard24

https://github.com/Alucard24/Alucard-Kernel-jfltexx/commit/c7d8067cd9702bb42d390dfb8394d0c053429506
https://github.com/Alucard24/Alucard-Kernel-jfltexx/commit/81fe075ee13e1f33ea8a92ead5441bda05eeafb3