arm64: tegra: Enable power and volume keys on Jetson TX1

Add a gpio-keys device tree node to represent the Power, Volume Up and
Volume Down keys found on Jetson TX1.
Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>

arch/arm64/boot/dts/nvidia/tegra210-p2597.dtsi

+#include <dt-bindings/input/input.h>
+
 / {
 	model = "NVIDIA Tegra210 P2597 I/O board";
 	compatible = "nvidia,p2597", "nvidia,tegra210";
@@ -1267,4 +1269,28 @@ sdhci@700b0000 {
 
 		cd-gpios = <&gpio TEGRA_GPIO(Z, 1) GPIO_ACTIVE_LOW>;
 	};
+
+	gpio-keys {
+		compatible = "gpio-keys";
+		label = "gpio-keys";
+
+		power {
+			label = "Power";
+			gpios = <&gpio TEGRA_GPIO(X, 5) GPIO_ACTIVE_LOW>;
+			linux,code = <KEY_POWER>;
+			wakeup-source;
+		};
+
+		volume_down {
+			label = "Volume Down";
+			gpios = <&gpio TEGRA_GPIO(Y, 0) GPIO_ACTIVE_LOW>;
+			linux,code = <KEY_VOLUMEDOWN>;
+		};
+
+		volume_up {
+			label = "Volume Up";
+			gpios = <&gpio TEGRA_GPIO(X, 6) GPIO_ACTIVE_LOW>;
+			linux,code = <KEY_VOLUMEUP>;
+		};
+	};
 };