Light On Back light only if off

Back light is set on at each key pressed if powersaving enabled - change
to only when off
Fix : same code is used for Ok button and Right Key

Fix : same code is used for Ok button and Right Key, change code to
allow right key to send UI_ACTION_RIGHT_KEY instead of UI_ACTION_OK, but
keep same logic in main loop for now, this will allow to use right key
for selection in futur code instead of having 2 keys with same function.