riscv: ae350: dts: Add SPDX license header

The SPDX license header is currently missing. Add one.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Leo Yu-Chi Liang <ycliang@andestech.com>
Reviewed-by: Rick Chen <rick@andestech.com>

arch/riscv/dts/ae350_32.dts

@@ -1,3 +1,5 @@
+// SPDX-License-Identifier: (GPL-2.0 OR MIT)
+
 /dts-v1/;
 
 #include "binman.dtsi"

arch/riscv/dts/ae350_64.dts

@@ -1,3 +1,5 @@
+// SPDX-License-Identifier: (GPL-2.0 OR MIT)
+
 /dts-v1/;
 
 #include "binman.dtsi"