license: add spdx identifier to all files

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: Ifddd07cc0eb5edeb2dcb410747073d68c6631cb1
diff --git a/tests/msgbuf_generic.c b/tests/msgbuf_generic.c
index d79d442..3307917 100644
--- a/tests/msgbuf_generic.c
+++ b/tests/msgbuf_generic.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later */
 /* Test pldm_msgbuf_extract() separately because we can't do _Generic() in C++
  * code, i.e. gtest */