Save value to shared prefs in HW value scale.

Otherwise we can run into precision issues if the HW e.g. uses a 0..255
scale.

Change-Id: I2df81db728faa64ee7b09cc3101122ff5c95b7a3
Merge branch 'cm-10.2' of git://github.com/CyanogenMod/android_packages_apps_Settings into cm-10.2