arm: dts: sun8i-t113s-mangopi-mq-r-t113: Add SPI NAND node

The Mango Pi MQ R has an unpopulated spot for a SPI NAND chip.
Add it to the device tree so I can use it.

arch/arm/dts/sun8i-t113s-mangopi-mq-r-t113.dts

@@ -33,3 +33,30 @@
 		interrupt-names = "host-wake";
 	};
 };
+
+&spi0 {
+	pinctrl-0 = <&spi0_pins>;
+	pinctrl-names = "default";
+	status = "okay";
+
+	flash@0 {
+		compatible = "spi-nand";
+		reg = <0>;
+
+		partitions {
+			compatible = "fixed-partitions";
+			#address-cells = <1>;
+			#size-cells = <1>;
+
+			partition@0 {
+				label = "uboot";
+				reg = <0x00000000 0x00080000>;
+			};
+
+			partition@80000 {
+				label = "ubi";
+				reg = <0x00080000 0x0fb00000>;
+			};
+		};
+	};
+};