arm64: dts: rockchip: Add recovery key support for rk3328-evb

Define recovery key for uboot if uboot used kernel dtb

Change-Id: Iad91e1ba5109c82512d125981f0a26aa6cf1ddc2
Signed-off-by: Zain Wang <wzz@rock-chips.com>

arch/arm64/boot/dts/rockchip/rk3328-evb.dts

@@ -15,6 +15,20 @@
 		stdout-path = "serial2:1500000n8";
 	};
 
+	adc-keys {
+		compatible = "adc-keys";
+		io-channels = <&saradc 0>;
+		io-channel-names = "buttons";
+		poll-interval = <100>;
+		keyup-threshold-microvolt = <1800000>;
+
+		vol-up-key {
+			linux,code = <KEY_VOLUMEUP>;
+			label = "volume up";
+			press-threshold-microvolt = <18000>;
+		};
+	};
+
 	dc_12v: dc-12v {
 		compatible = "regulator-fixed";
 		regulator-name = "dc_12v";
@@ -487,6 +501,11 @@
 	status = "okay";
 };
 
+&saradc {
+	status = "okay";
+	vref-supply = <&vcc_18>;
+};
+
 &sdio {
 	bus-width = <4>;
 	cap-sd-highspeed;