settings: performance: Update get current values in Processor view

Some users have been complaining about min/max frequency being
set incorrectly on some CM builds.

One way that they could be seeing this is by using the Processor
Performance information in Settings which seems to load the values
for min/max frequency and governor once and then never reloads
them unless you change the actual setting.

This is easy to see by changing the values yourself by modifying
the /sys files directly.

With this commit, changing the /sys files will cause the
Performance view to show the correct values, not the cache values.

Change-Id: I96719e4f40081cb8d2c9b1fd63a32332823cf77d