Setup overlay for single-color notification LED.

Remove option to change color of notification LED as it is single-color.

This relies on Ayysir's following commits. Do not merge first!!!

Add support for single color notification LED (1/2)
http://gerrit.aospal.com/#/c/296/

Add support for single color notification LED (2/2)
http://gerrit.aospal.com/#/c/295/