tests: Move to kernel style SPDX license identifiers The SPDX identifier is a legally binding shorthand, which can be used instead of the full boiler plate text. See https://spdx.org/ids-how for details. Signed-off-by: Michael Jeanson <mjeanson@efficios.com> Change-Id: I89cd4b4b7440f71f52426a5508252932bb46e796 Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>