arm64: dts: imx8mm-emcon-avari: Fix gpio-cells

Per nxp,pcf8575.yaml, #gpio-cells should be 2.

Change it to fix the following schema warning:

imx8mm-emcon-avari.dtb: gpio@3a: #gpio-cells:0:0: 2 was expected
	from schema $id: http://devicetree.org/schemas/gpio/nxp,pcf8575.yaml#Signed-off-by: Fabio Estevam <festevam@denx.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm64/boot/dts/freescale/imx8mm-emcon-avari.dtsi

@@ -104,7 +104,7 @@ boardID: gpio@3a {
 		compatible = "nxp,pca8574";
 		reg = <0x3a>;
 		gpio-controller;
-		#gpio-cells = <1>;
+		#gpio-cells = <2>;
 	};
 };