Revert "Add DevicePerformanceSettingsHelper"

Possibly a simpler and a cleaner solution: https://github.com/namagi/android_packages_apps_Settings/commit/c698ddf7fc23083615729f768e01b50a5d7430e2

unfortunately I can't make a pull request for that as there is no Seetings project on razrqcom.
The above mentioned solution seems simpler and avoids adding an extra apk to the system.

Also, that patch by Emerson requires a device to be rebooted for the thermal_max_freq and scaling_max_freq to be in sync which is really a bad requirement for scaling frequencies.
Need for superuer access is also not needed.