arm: dts: rockchip: rk3399: add and enable rng node

Add rng node in rk3399-u-boot.dtsi and enable it in
rk3399-evb-u-boot.dtsi.

Signed-off-by: Lin Jinhan <troy.lin@rock-chips.com>
Tested-by: Peter Robinson <pbrobinson@gmail.com>
Reviewed-by: Sughosh Ganu <sughosh.ganu@linaro.org>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
diff --git a/arch/arm/dts/rk3399-evb-u-boot.dtsi b/arch/arm/dts/rk3399-evb-u-boot.dtsi
index ccb33d3..f68a56f 100644
--- a/arch/arm/dts/rk3399-evb-u-boot.dtsi
+++ b/arch/arm/dts/rk3399-evb-u-boot.dtsi
@@ -11,3 +11,7 @@
 		u-boot,spl-boot-order = &sdhci, &sdmmc;
 	};
 };
+
+&rng {
+	status = "okay";
+};