drm/rockchip: rgb: update SPDX license identifier

Update SPDX License Identifier from GPL-2.0+ to GPL-2.0
and drop some GPL text.
This fixes a mismatch between the existing SPDX headers and GPL
boilerplate text.

Fixes: 1f0f0151 ("Add support for Rockchip Soc RGB output interface")
Cc: stable@vger.kernel.org
Reported-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sandy Huang <hjc@rock-chips.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://patchwork.freedesktop.org/patch/msgid/1548238479-171491-1-git-send-email-hjc@rock-chips.com

drivers/gpu/drm/rockchip/rockchip_rgb.c

-//SPDX-License-Identifier: GPL-2.0+
+// SPDX-License-Identifier: GPL-2.0
 /*
  * Copyright (C) Fuzhou Rockchip Electronics Co.Ltd
  * Author:
  *      Sandy Huang <hjc@rock-chips.com>
- *
- * This software is licensed under the terms of the GNU General Public
- * License version 2, as published by the Free Software Foundation, and
- * may be copied, distributed, and modified under those terms.
- *
- * This program 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.
  */
 
 #include <drm/drmP.h>

drivers/gpu/drm/rockchip/rockchip_rgb.h

-//SPDX-License-Identifier: GPL-2.0+
+/* SPDX-License-Identifier: GPL-2.0 */
 /*
  * Copyright (C) Fuzhou Rockchip Electronics Co.Ltd
  * Author:
  *      Sandy Huang <hjc@rock-chips.com>
- *
- * This software is licensed under the terms of the GNU General Public
- * License version 2, as published by the Free Software Foundation, and
- * may be copied, distributed, and modified under those terms.
- *
- * This program 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.
  */
 
 #ifdef CONFIG_ROCKCHIP_RGB