rockchip: rk3399: Add Nanopi M4 2GB board support

commit b2f5da9dd068 ("rockchip: rk3399: Add Nanopi M4 board support") added
support for Nanopi M4 board with Dual-Channel 4GB LPDDR3-1866 RAM.
This patch adds another variant of NanoPi M4 board with Dual-Channel
2GB DDR3-1866 RAM.

Signed-off-by: Deepak Das <deepakdas.linux@gmail.com>
diff --git a/arch/arm/dts/rk3399-nanopi-m4-2gb-u-boot.dtsi b/arch/arm/dts/rk3399-nanopi-m4-2gb-u-boot.dtsi
new file mode 100644
index 0000000..a2f9786
--- /dev/null
+++ b/arch/arm/dts/rk3399-nanopi-m4-2gb-u-boot.dtsi
@@ -0,0 +1,8 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2019 Jagan Teki <jagan@amarulasolutions.com>
+ * Copyright (C) 2020 Deepak Das <deepakdas.linux@gmail.com>
+ */
+
+#include "rk3399-nanopi4-u-boot.dtsi"
+#include "rk3399-sdram-ddr3-1866.dtsi"