Manage button and keyboard backlights with light sensor in both manual and automatic mode.

Now the manual brightness mode only applies to the LCD backlight and
button and keyboard backlights are always managed automatically.

Fixes bug b/2195798 (Passion capacitive key backlights don't always come on)

This change only affects the framework based auto-brightness implementation.
Hardware auto-brightness is not affected.

Change-Id: Ib88310d642d498591e8879c8269d630ff3f7c8af
Signed-off-by: Mike Lockwood <lockwood@android.com>