set backlight to 0 if backlight switch is off

- this is to ensure the backlight stays off when the
panel is off to avoid flickering

Change-Id: I180a76c8283aa1c4a3f7d0c42dfc7934e3f03524
Revert "set backlight to 0 if backlight switch is off"

This reverts commit 8a41fb67b289492f9a0fad13a6b9a15d167b2977.