ARM: mstar: Add common dtsi for SSD201/SSD202D

The SSD201 and SSD202D are basically the same chip with a different DDR die
packaged (64MB DDR2 or 128MB DDR3).

This patch adds a shared dtsi for the common parts of these chips like
gpio, pinctrl etc.

Signed-off-by: Daniel Palmer <daniel@0x0f.com>
Link: https://lore.kernel.org/r/20201201134330.3037007-6-daniel@0x0f.com'
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

arch/arm/boot/dts/mstar-infinity2m-ssd20xd.dtsi

@@ -0,0 +1,7 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2020 thingy.jp.
+ * Author: Daniel Palmer <daniel@thingy.jp>
+ */
+
+#include "mstar-infinity2m.dtsi"