Add support to cpufreq
Add support to cpufreq on mt8188.
Depends on: trusted-firmware-a!25 (closed)
Test:
i700_evk:/ # cat /sys/devices/system/cpu/cpufreq/policy0/scaling_available_governors
conservative powersave performance schedutil
i700_evk:/ # cat /sys/devices/system/cpu/cpufreq/policy6/scaling_available_governors
conservative powersave performance schedutil