ARM: dts: imx: add Boundary Devices Nitrogen6_SoloX board

Based on i.MX6 SoloX with 1GB of RAM.

https://boundarydevices.com/product/nit6_solox-imx6/Signed-off-by: Gary Bisson <gary.bisson@boundarydevices.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm/boot/dts/Makefile

@@ -377,6 +377,7 @@ dtb-$(CONFIG_SOC_IMX6SL) += \
 	imx6sl-evk.dtb \
 	imx6sl-warp.dtb
 dtb-$(CONFIG_SOC_IMX6SX) += \
+	imx6sx-nitrogen6sx.dtb \
 	imx6sx-sabreauto.dtb \
 	imx6sx-sdb-reva.dtb \
 	imx6sx-sdb.dtb