arm64: dts: rockchip: remove enable-gpio of backlight on rk3399 evb

There is no enable-gpio for backlight control on rk3399 evb,
actually GPIO1_B5 is for LCD panle enable. So remove it from backlight
dt node.

Signed-off-by: Andy Yan <andy.yan@rock-chips.com>
Link: https://lore.kernel.org/r/20200305113912.32226-4-andy.yan@rock-chips.com


Signed-off-by: Heiko Stuebner <heiko@sntech.de>