KDbusAddons: Convert license statement to SPDX
Summary:
Convert license statements to SPDX and add license
files as required by REUSE.
Reviewers: cgiboudeaux
Reviewed By: cgiboudeaux
Subscribers: kde-frameworks-devel
Tags: Frameworks
Maniphest Tasks: T11550
Differential Revision: https://phabricator.kde.org/D27602