init: Enable backlight trigger for LCD

Disable backlight when blanked out.

Ref: CRACKLING-626
Change-Id: Ifc698c1470b086b0e1f083c3c234f272988d108c

rootdir/etc/init.target.rc

@@ -25,6 +25,10 @@
 # ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #
 
+on early-init
+    # Turn off backlight on blank
+    write /sys/class/leds/lcd-backlight/trigger "backlight"
+
 on boot
     # charger
     chown system system /sys/bus/i2c/drivers/lc709203/batt_capacity