rockchip: dts: Enable SARADC for rk3399-evb

Enable the SARADC for download key pressed detect.

Signed-off-by: David Wu <david.wu@rock-chips.com>
Acked-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>

arch/arm/dts/rk3399-evb.dts

@@ -149,6 +149,10 @@
 	status = "okay";
 };
 
+&saradc {
+	status = "okay";
+};
+
 &sdmmc {
 	bus-width = <4>;
 	status = "okay";