udoo-neo: Convert to OF_UPSTREAM

Instead of using the local imx6sx-udoo-neo  devicetree copies from U-Boot,
convert the imx6sx-udoo-neo boards to OF_UPSTREAM so that the upstream
kernel devicetrees can be used instead.

Tested on a imx6sx-udoo-neo-full board.

Signed-off-by: Fabio Estevam <festevam@gmail.com>
diff --git a/arch/arm/dts/Makefile b/arch/arm/dts/Makefile
index 7265e55..a4d95c8 100644
--- a/arch/arm/dts/Makefile
+++ b/arch/arm/dts/Makefile
@@ -840,10 +840,7 @@
 dtb-$(CONFIG_MX6SX) += \
 	imx6sx-sabreauto.dtb \
 	imx6sx-sdb.dtb \
-	imx6sx-softing-vining-2000.dtb \
-	imx6sx-udoo-neo-basic.dtb \
-	imx6sx-udoo-neo-extended.dtb \
-	imx6sx-udoo-neo-full.dtb
+	imx6sx-softing-vining-2000.dtb
 
 dtb-$(CONFIG_MX6UL) += \
 	imx6ul-geam.dtb \