board: Add support for Sielaff i.MX6 Solo board

The Sielaff i.MX6 Solo board is a control and HMI board for vending
machines. Add support for this board.

The devicetree files are taken from pending changes in the Linux
kernel that are available from linux-next and will likely be
part of Linux v6.9.

Signed-off-by: Frieder Schrempf <frieder.schrempf@kontron.de>
diff --git a/arch/arm/dts/Makefile b/arch/arm/dts/Makefile
index ce10d3d..1400d02 100644
--- a/arch/arm/dts/Makefile
+++ b/arch/arm/dts/Makefile
@@ -930,6 +930,7 @@
 	imx6dl-riotboard.dtb \
 	imx6dl-sabreauto.dtb \
 	imx6dl-sabresd.dtb \
+	imx6dl-sielaff.dtb \
 	imx6dl-wandboard-revd1.dtb \
 	imx6s-dhcom-drc02.dtb