Galaxy S III settings: Add support for keyboard backlight

Add support for keyboard backlight on Samsung MSM8960 devices
with a hard keyboard, such as the Galaxy S Relay 4G.

Change-Id: I0ec245e39315d782f4429490f84a9f9227c556a4
Merge branch 'cm-10.1' of github.com:CyanogenMod/android_device_samsung_msm8960-common into jb-mr1