ARM: dts: imx6qdl-nitrogen6x: Add SPI NOR partitions

This adds the partitions definition for the SPI NOR to provide
backward compatibility with the documented[1] layout used with
Boundary Devices BSP.

1. https://boundarydevices.com/boot-flash-access-linux/

It exports to Linux:

 mtd0: bootloader
 mtd1: env
 mtd2: splash
Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>
Reviewed-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm/boot/dts/imx6qdl-nitrogen6x.dtsi

@@ -276,6 +276,23 @@ flash: m25p80@0 {
 		compatible = "sst,sst25vf016b", "jedec,spi-nor";
 		spi-max-frequency = <20000000>;
 		reg = <0>;
+		#address-cells = <1>;
+		#size-cells = <1>;
+
+		partition@0 {
+			label = "bootloader";
+			reg = <0x0 0xc0000>;
+		};
+
+		partition@c0000 {
+			label = "env";
+			reg = <0xc0000 0x2000>;
+		};
+
+		partition@c2000 {
+			label = "splash";
+			reg = <0xc2000 0x13e000>;
+		};
 	};
 };