With the backlight phandle the driver can manage the backlight on/off in
sync with the panel enable/disable.
Signed-off-by: NPeter Ujfalusi <peter.ujfalusi@ti.com>
Reviewed-by: NTomi Valkeinen <tomi.valkeinen@ti.com>
Signed-off-by: NTony Lindgren <tony@atomide.com>