ARM: dts: imx6sx: update gpmi #size-cells to 0

Update gpmi #size-cells to 0 to fix below CHECK_DTB warnings:
  arch/arm/boot/dts/nxp/imx/imx6sx-nitrogen6sx.dtb: nand-controller@1806000 (fsl,imx6sx-gpmi-nand): #size-cells: 0 was expected
        from schema $id: http://devicetree.org/schemas/mtd/gpmi-nand.yaml#

Signed-off-by: Frank Li <Frank.Li@nxp.com>
Reviewed-by: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

Author: nxpfrankli

arch/arm/boot/dts/nxp/imx/imx6sx.dtsi

@@ -224,7 +224,7 @@
 		gpmi: nand-controller@1806000 {
 			compatible = "fsl,imx6sx-gpmi-nand";
 			#address-cells = <1>;
-			#size-cells = <1>;
+			#size-cells = <0>;
 			reg = <0x01806000 0x2000>, <0x01808000 0x4000>;
 			reg-names = "gpmi-nand", "bch";
 			interrupts = <GIC_SPI 15 IRQ_TYPE_LEVEL_HIGH>;