arm: mvebu: Add Allied Telesis x220

Add the Allied Telesis x220 board. There are a number of other variants
with the same CPU block that are sold under some different brand names
but the x220 was first.

The x220 uses the AlleyCat3 switch chip with integrated ARMv7 CPU.
Because of this it is reliant on a binary blob for the DDR training. In
upstream u-boot this is replaced by an empty file.

Signed-off-by: Chris Packham <judge.packham@gmail.com>
Reviewed-by: Stefan Roese <stefan.roese@mailbox.org>

include/configs/x220.h

@@ -0,0 +1,20 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Copyright (C) 2025 Allied Telesis Labs
+ */
+
+#ifndef _CONFIG_X220_H
+#define _CONFIG_X220_H
+
+/* Keep device tree and initrd in lower memory so the kernel can access them */
+#define CFG_EXTRA_ENV_SETTINGS	\
+	"fdt_high=0x10000000\0"		\
+	"initrd_high=0x10000000\0"
+
+/*
+ * mv-common.h should be defined after CMD configs since it used them
+ * to enable certain macros
+ */
+#include "mv-common.h"
+
+#endif /* _CONFIG_X220_H */