test: dfu: cosmetic: Add missing license information to DFU test scripts

By mistake I've forgotten to add the SPDX license tags for the DFU testing
scripts.
This commit fixes that and also provides some other relevant information.

Signed-off-by: Lukasz Majewski <l.majewski@samsung.com>
Acked-by: Stephen Warren <swarren@nvidia.com>
diff --git a/test/dfu/dfu_gadget_test.sh b/test/dfu/dfu_gadget_test.sh
index 4133155..2f5b7db 100755
--- a/test/dfu/dfu_gadget_test.sh
+++ b/test/dfu/dfu_gadget_test.sh
@@ -1,5 +1,15 @@
 #! /bin/bash
 
+# Copyright (C) 2014 Samsung Electronics
+# Lukasz Majewski <l.majewski@samsung.com>
+#
+# Script fixes, enhancements and testing:
+# Stephen Warren <swarren@nvidia.com>
+#
+# DFU operation test script
+#
+# SPDX-License-Identifier:	GPL-2.0+
+
 set -e # any command return if not equal to zero
 clear