ARM: dts: imx28-tx28: add SPDX-License-Identifier

Replace the license blob by a clean SPDX-License-Identifier with GPL2
or MIT even if X11 is specified in the original blob since the actual
license text corresponds to a MIT license.
Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Cc: Lothar Waßmann <LW@KARO-electronics.de>
Acked-by: Lothar Waßmann <LW@KARO-electronics.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm/boot/dts/imx28-tx28.dts

+// SPDX-License-Identifier: GPL-2.0 OR MIT
 /*
  * Copyright 2012 Shawn Guo <shawn.guo@linaro.org>
  * Copyright 2013-2017 Lothar Waßmann <LW@KARO-electronics.de>
- *
- * This file is dual-licensed: you can use it either under the terms
- * of the GPL or the X11 license, at your option. Note that this dual
- * licensing only applies to this file, and not this project as a
- * whole.
- *
- *  a) This file is free software; you can redistribute it and/or
- *     modify it under the terms of the GNU General Public License
- *     version 2 as published by the Free Software Foundation.
- *
- *     This file 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 General Public License for more details.
- *
- * Or, alternatively,
- *
- *  b) Permission is hereby granted, free of charge, to any person
- *     obtaining a copy of this software and associated documentation
- *     files (the "Software"), to deal in the Software without
- *     restriction, including without limitation the rights to use,
- *     copy, modify, merge, publish, distribute, sublicense, and/or
- *     sell copies of the Software, and to permit persons to whom the
- *     Software is furnished to do so, subject to the following
- *     conditions:
- *
- *     The above copyright notice and this permission notice shall be
- *     included in all copies or substantial portions of the Software.
- *
- *     THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
- *     EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
- *     OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
- *     NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
- *     HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
- *     WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
- *     FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
- *     OTHER DEALINGS IN THE SOFTWARE.
  */
 
 /dts-v1/;