Revert "Revert "cpufreq: create a helper function to get CPU utilization. Picked from @stratosk""

This reverts commit deab3db5de9dde9dea2c6b3b39f42e3d2c45d4dd.
Revert "Revert "cpufreq: Initial CPU utilization should be 0""

This reverts commit 2e5f062964926064a56796123d4f8ff73ba627eb.