Use SPDX identifiers

SPDX identifiers are simpler, and reduce the amount of cruft we have in
code files.  They are recommended by linux foundation, and therefore we
should do as they allow.

This patchset does not intend to modify any intent on any existing
copyrights or licenses, only to standardize their inclusion.

[1] https://www.linuxfoundation.org/blog/blog/copyright-notices-in-open-source-software-projects

Change-Id: I935c7c0156caa78fc368c929cebd0f068031e830
Signed-off-by: Ed Tanous <etanous@nvidia.com>
diff --git a/include/duplicatable_file_handle.hpp b/include/duplicatable_file_handle.hpp
index 6d2514e..9532312 100644
--- a/include/duplicatable_file_handle.hpp
+++ b/include/duplicatable_file_handle.hpp
@@ -1,3 +1,5 @@
+// SPDX-License-Identifier: Apache-2.0
+// SPDX-FileCopyrightText: Copyright OpenBMC Authors
 #include <boost/beast/core/file_posix.hpp>
 
 struct DuplicatableFileHandle