drm/panel: seiko-43wvf1g: Switch to SPDX identifier

Adopt the SPDX license identifier headers to ease license compliance
management.
Signed-off-by: NFabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: NThierry Reding <treding@nvidia.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1532575167-14754-1-git-send-email-festevam@gmail.com

drivers/gpu/drm/panel/panel-seiko-43wvf1g.c

+// SPDX-License-Identifier: GPL-2.0
 /*
  * Copyright (C) 2017 NXP Semiconductors.
  * Author: Marco Franchi <marco.franchi@nxp.com>
  *
  * Based on Panel Simple driver by Thierry Reding <treding@nvidia.com>
- *
- * This program 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.
  */
 
 #include <linux/backlight.h>