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/board/sielaff/imx6dl-sielaff/Makefile b/board/sielaff/imx6dl-sielaff/Makefile
new file mode 100644
index 0000000..65cecfe
--- /dev/null
+++ b/board/sielaff/imx6dl-sielaff/Makefile
@@ -0,0 +1,8 @@
+# SPDX-License-Identifier: GPL-2.0+
+# (C) Copyright 2022 Kontron Electronics GmbH
+
+ifdef CONFIG_SPL_BUILD
+obj-y := spl.o
+else
+obj-y := imx6dl-sielaff.o
+endif