spi: rockchip: add bindings for rk3399 spi

Add devicetree bindings for Rockchip rk3399 spi which found on
Rockchip rk3399 SoCs.

Signed-off-by: Jianqun Xu <jay.xu@rock-chips.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-rockchip.c

@@ -866,6 +866,7 @@ static const struct of_device_id rockchip_spi_dt_match[] = {
 	{ .compatible = "rockchip,rk3066-spi", },
 	{ .compatible = "rockchip,rk3188-spi", },
 	{ .compatible = "rockchip,rk3288-spi", },
+	{ .compatible = "rockchip,rk3399-spi", },
 	{ },
 };
 MODULE_DEVICE_TABLE(of, rockchip_spi_dt_match);