Fix license headers for tablet v2 interfaces

We use SPDX license markers in kwayland-server.

src/server/tablet_v2_interface.cpp

-/********************************************************************
-Copyright 2019 Aleix Pol Gonzalez <aleixpol@kde.org>
-
-This library is free software; you can redistribute it and/or
-modify it under the terms of the GNU Lesser General Public
-License as published by the Free Software Foundation; either
-version 2.1 of the License, or (at your option) version 3, or any
-later version accepted by the membership of KDE e.V. (or its
-successor approved by the membership of KDE e.V.), which shall
-act as a proxy defined in Section 6 of version 3 of the license.
-
-This library is distributed in the hope that it will be useful,
-but WITHOUT ANY WARRANTY; without even the implied warranty of
-MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-Lesser General Public License for more details.
-
-You should have received a copy of the GNU Lesser General Public
-License along with this library.  If not, see <http://www.gnu.org/licenses/>.
-*********************************************************************/
+/*
+    SPDX-FileCopyrightText: 2019 Aleix Pol Gonzalez <aleixpol@kde.org>
+
+    SPDX-License-Identifier: LGPL-2.1-only OR LGPL-3.0-only OR LicenseRef-KDE-Accepted-LGPL
+*/
+
 #include "tablet_v2_interface.h"
 #include "display.h"
 #include "seat_interface.h"

src/server/tablet_v2_interface.h

-/********************************************************************
-Copyright 2019 Aleix Pol Gonzalez <aleixpol@kde.org>
-
-This library is free software; you can redistribute it and/or
-modify it under the terms of the GNU Lesser General Public
-License as published by the Free Software Foundation; either
-version 2.1 of the License, or (at your option) version 3, or any
-later version accepted by the membership of KDE e.V. (or its
-successor approved by the membership of KDE e.V.), which shall
-act as a proxy defined in Section 6 of version 3 of the license.
-
-This library is distributed in the hope that it will be useful,
-but WITHOUT ANY WARRANTY; without even the implied warranty of
-MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-Lesser General Public License for more details.
-
-You should have received a copy of the GNU Lesser General Public
-License along with this library.  If not, see <http://www.gnu.org/licenses/>.
-*********************************************************************/
+/*
+    SPDX-FileCopyrightText: 2019 Aleix Pol Gonzalez <aleixpol@kde.org>
+
+    SPDX-License-Identifier: LGPL-2.1-only OR LGPL-3.0-only OR LicenseRef-KDE-Accepted-LGPL
+*/
+
 #ifndef WAYLAND_SERVER_TABLET_INTERFACE_H
 #define WAYLAND_SERVER_TABLET_INTERFACE_H