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. Change-Id: I7c25a3bc48ee328500a604cb276877d4cadfa997 Signed-off-by: Michael Jeanson <mjeanson@efficios.com> Reviewed-on: https://review.lttng.org/c/babeltrace/+/3227 CI-Build: Philippe Proulx <eeppeliteloop@gmail.com> Tested-by: jenkins <jenkins@lttng.org> Reviewed-by: Philippe Proulx <eeppeliteloop@gmail.com>