arm64: dts: imx8mn: Fix NAND controller size-cells

The NAND controller size-cells should be 0 per DT bindings.
Fix the following warning produces by DT bindings check:
"
nand-controller@33002000: #size-cells:0:0: 0 was expected
nand-controller@33002000: Unevaluated properties are not allowed ('#address-cells', '#size-cells' were unexpected)
"

Fixes: 6c3debcb ("arm64: dts: freescale: Add i.MX8MN dtsi support")
Signed-off-by: Marek Vasut <marex@denx.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm64/boot/dts/freescale/imx8mn.dtsi

@@ -1102,7 +1102,7 @@ dma_apbh: dma-controller@33000000 {
 		gpmi: nand-controller@33002000 {
 			compatible = "fsl,imx8mn-gpmi-nand", "fsl,imx7d-gpmi-nand";
 			#address-cells = <1>;
-			#size-cells = <1>;
+			#size-cells = <0>;
 			reg = <0x33002000 0x2000>, <0x33004000 0x4000>;
 			reg-names = "gpmi-nand", "bch";
 			interrupts = <GIC_SPI 14 IRQ_TYPE_LEVEL_HIGH>;