license: add spdx identifier to all files

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: Ifddd07cc0eb5edeb2dcb410747073d68c6631cb1
diff --git a/src/requester/instance-id.c b/src/requester/instance-id.c
index a079f7b..108e451 100644
--- a/src/requester/instance-id.c
+++ b/src/requester/instance-id.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later */
 // NOLINTNEXTLINE(bugprone-reserved-identifier,cert-dcl37-c,cert-dcl51-cpp)
 #define _GNU_SOURCE
 #include "libpldm/instance-id.h"