adguardhome: add SPDX license identifiers

Add GPL 2.0 only SPDX license identifiers to Makefile and all scripts.

Signed-off-by: George Sapkin <george@sapk.in>

net/adguardhome/Makefile

@@ -1,7 +1,4 @@
-#
-# This is free software, licensed under the GNU General Public License v2.
-# See /LICENSE for more information.
-#
+# SPDX-License-Identifier: GPL-2.0-only
 
 include $(TOPDIR)/rules.mk
 

net/adguardhome/files/adguardhome.defaults

@@ -1,4 +1,6 @@
 #!/bin/sh
+#
+# SPDX-License-Identifier: GPL-2.0-only
 
 # Migrate old config format only
 OLD_CONFIG_FILE=$(uci -q get adguardhome.config.config)

net/adguardhome/files/adguardhome.init

@@ -1,4 +1,7 @@
 #!/bin/sh /etc/rc.common
+#
+# SPDX-License-Identifier: GPL-2.0-only
+#
 # shellcheck disable=SC3043 # ash supports local
 
 PROG=/usr/bin/AdGuardHome

net/adguardhome/test.sh

@@ -1,3 +1,5 @@
 #!/bin/sh
+#
+# SPDX-License-Identifier: GPL-2.0-only
 
 AdGuardHome --version | grep -F "$PKG_VERSION"