src/confd: add SPDX license identifier to new files

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

src/confd/src/core.h

@@ -1,4 +1,5 @@
 /* SPDX-License-Identifier: BSD-3-Clause */
+
 #ifndef CONFD_CORE_H_
 #define CONFD_CORE_H_
 

src/confd/src/sr_ext.c

@@ -1,3 +1,5 @@
+/* SPDX-License-Identifier: BSD-3-Clause */
+
 #include <libyang/libyang.h>
 
 #include "sr_ext.h"

src/confd/src/sr_ext.h

@@ -1,3 +1,5 @@
+/* SPDX-License-Identifier: BSD-3-Clause */
+
 #ifndef CONFD_SR_EXT_H_
 #define CONFD_SR_EXT_H_