arm64: dts: rockchip: add GRF GPIO controller to rk3328

Adding a GRF GPIO controller labled "grf_gpio" to rk3328, currently
providing access to the GPIO_MUTE pin, which is manupulated by the
GRF_SOC_CON10 register.

The GPIO_MUTE pin is referred to as <&grf_gpio 0>.

Signed-off-by: Levin Du <djw@t-chip.com.cn>
[dropped default-status disabled]
Signed-off-by: Heiko Stuebner <heiko@sntech.de>

arch/arm64/boot/dts/rockchip/rk3328.dtsi

@@ -249,6 +249,12 @@
 			status = "disabled";
 		};
 
+		grf_gpio: grf-gpio {
+			compatible = "rockchip,rk3328-grf-gpio";
+			gpio-controller;
+			#gpio-cells = <2>;
+		};
+
 		power: power-controller {
 			compatible = "rockchip,rk3328-power-controller";
 			#power-domain-cells = <1>;
@@ -274,7 +280,6 @@
 			mode-bootloader = <BOOT_FASTBOOT>;
 			mode-loader = <BOOT_BL_DOWNLOAD>;
 		};
-
 	};
 
 	uart0: serial@ff110000 {