keyboard: re-add code to detect lid state

This was lost in the cm-11 merge. Without this, a change in lid state
isn't generated to light up the keyboard backlight

Change-Id: Ief35cebcb62da13afe1ae7531d69ab58e196be9e
Merge "keyboard: re-add code to detect lid state" into kitkat
Merge "keyboard: re-add code to detect lid state" into kitkaty
Merge commit '99d408794423da33bb60e9d0b559277ccc8876b6' into kitkat