rockchip: dts: Enable SARADC for rk3288-popmetal

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/rk3288-popmetal.dtsi

@@ -491,6 +491,10 @@
 	};
 };
 
+&saradc {
+	status = "okay";
+};
+
 &tsadc {
 	rockchip,hw-tshut-mode = <0>;
 	rockchip,hw-tshut-polarity = <0>;