imx: imx6ul: Add support for Kontron Electronics SL/BL i.MX6UL/ULL boards (N63xx/N64xx)

This adds support for i.MX6UL/ULL-based evaluation kits with SoMs by
Kontron Electronics GmbH.

Currently there are the following SoM flavors (SoM-Line):
  * N6310: SOM with i.MX6UL-2, 256MB RAM, 256MB SPI NAND
  * N6311: SOM with i.MX6UL-2, 512MB RAM, 512MB SPI NAND
  * N6411: SOM with i.MX6ULL, 512MB RAM, 512MB SPI NAND

And the according evaluation boards (Board-Line):
  * N6310-S: Baseboard with SOM N6310, eMMC, display (optional), ...
  * N6311-S: Baseboard with SOM N6311, eMMC, display (optional), ...
  * N6411-S: Baseboard with SOM N6411, eMMC, display (optional), ...

Currently U-Boot describes i.MX6UL and i.MX6ULL through separate config
options at compile-time. Though the differences are so minor, that for
the scope of these SoMs we just use a single defconfig that is compatible
with both SoCs.

Signed-off-by: Frieder Schrempf <frieder.schrempf@kontron.de>
Reviewed-by: Stefano Babic <sbabic@denx.de>
diff --git a/arch/arm/dts/imx6ul-kontron-n631x-som.dtsi b/arch/arm/dts/imx6ul-kontron-n631x-som.dtsi
new file mode 100644
index 0000000..9a11798
--- /dev/null
+++ b/arch/arm/dts/imx6ul-kontron-n631x-som.dtsi
@@ -0,0 +1,14 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2017 exceet electronics GmbH
+ * Copyright (C) 2018 Kontron Electronics GmbH
+ * Copyright (c) 2019 Krzysztof Kozlowski <krzk@kernel.org>
+ */
+
+#include "imx6ul.dtsi"
+#include "imx6ul-kontron-n6x1x-som-common.dtsi"
+
+/ {
+	model = "Kontron N631X SOM";
+	compatible = "kontron,imx6ul-n631x-som", "fsl,imx6ul";
+};