arm64: dts: sc9860: move GPIO keys to board

GPIO keys are properties of a board, not SoC, because SoC physically
does not have any keys or buttons.

This also fixes dtc W=1 build warning:

  sc9860.dtsi:688.13-714.5: Warning (simple_bus_reg): /soc/gpio-keys: missing or empty reg/ranges property
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Link: https://lore.kernel.org/r/20240401141128.98317-2-krzk@kernel.org

arch/arm64/boot/dts/sprd/sc9860.dtsi

@@ -684,33 +684,5 @@ etm7_out: endpoint {
 				};
 			};
 		};
-
-		gpio-keys {
-			compatible = "gpio-keys";
-
-			key-volumedown {
-				label = "Volume Down Key";
-				linux,code = <KEY_VOLUMEDOWN>;
-				gpios = <&eic_debounce 2 GPIO_ACTIVE_LOW>;
-				debounce-interval = <2>;
-				wakeup-source;
-			};
-
-			key-volumeup {
-				label = "Volume Up Key";
-				linux,code = <KEY_VOLUMEUP>;
-				gpios = <&pmic_eic 10 GPIO_ACTIVE_HIGH>;
-				debounce-interval = <2>;
-				wakeup-source;
-			};
-
-			key-power {
-				label = "Power Key";
-				linux,code = <KEY_POWER>;
-				gpios = <&pmic_eic 1 GPIO_ACTIVE_HIGH>;
-				debounce-interval = <2>;
-				wakeup-source;
-			};
-		};
 	};
 };

arch/arm64/boot/dts/sprd/sp9860g-1h10.dts

@@ -34,6 +34,34 @@ chosen {
 		stdout-path = "serial1:115200n8";
 	};
 
+	gpio-keys {
+		compatible = "gpio-keys";
+
+		key-volumedown {
+			label = "Volume Down Key";
+			linux,code = <KEY_VOLUMEDOWN>;
+			gpios = <&eic_debounce 2 GPIO_ACTIVE_LOW>;
+			debounce-interval = <2>;
+			wakeup-source;
+		};
+
+		key-volumeup {
+			label = "Volume Up Key";
+			linux,code = <KEY_VOLUMEUP>;
+			gpios = <&pmic_eic 10 GPIO_ACTIVE_HIGH>;
+			debounce-interval = <2>;
+			wakeup-source;
+		};
+
+		key-power {
+			label = "Power Key";
+			linux,code = <KEY_POWER>;
+			gpios = <&pmic_eic 1 GPIO_ACTIVE_HIGH>;
+			debounce-interval = <2>;
+			wakeup-source;
+		};
+	};
+
 	reserved-memory {
 		#address-cells = <2>;
 		#size-cells = <2>;