arm64: tegra: Add GPIO keys on P2771

The P2771 has three keys (power, volume up and volume down) that are
connected to pins on the AON GPIO controller.
Acked-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>

arch/arm64/boot/dts/nvidia/tegra186-p2771-0000.dts

 /dts-v1/;
 
+#include <dt-bindings/input/linux-event-codes.h>
+
 #include "tegra186-p3310.dtsi"
 
 / {
@@ -13,6 +15,38 @@ sdhci@3400000 {
 		vmmc-supply = <&vdd_sd>;
 	};
 
+	gpio-keys {
+		compatible = "gpio-keys";
+
+		power {
+			label = "Power";
+			gpios = <&gpio_aon TEGRA_AON_GPIO(FF, 0)
+					   GPIO_ACTIVE_LOW>;
+			linux,input-type = <EV_KEY>;
+			linux,code = <KEY_POWER>;
+			debounce-interval = <10>;
+			wakeup-source;
+		};
+
+		volume-up {
+			label = "Volume Up";
+			gpios = <&gpio_aon TEGRA_AON_GPIO(FF, 1)
+					   GPIO_ACTIVE_LOW>;
+			linux,input-type = <EV_KEY>;
+			linux,code = <KEY_VOLUMEUP>;
+			debounce-interval = <10>;
+		};
+
+		volume-down {
+			label = "Volume Down";
+			gpios = <&gpio_aon TEGRA_AON_GPIO(FF, 2)
+					   GPIO_ACTIVE_LOW>;
+			linux,input-type = <EV_KEY>;
+			linux,code = <KEY_VOLUMEDOWN>;
+			debounce-interval = <10>;
+		};
+	};
+
 	regulators {
 		vdd_sd: regulator@100 {
 			compatible = "regulator-fixed";