Remove CPU file updating code.

The method of capping CPU frequencies that battery saver was using isn't
supported. Remove the current CPU frequency capping code for now.

Bug: 79580230
Bug: 187909008
Test: atest frameworks/base/services/tests/servicestests/src/com/android/server/power/batterysaver
Test: atest CtsBatterySavingTestCases
Change-Id: Ib5ecad2e98e4620a758f8db21cf39485d2f923c1