media: rcar_drif: convert to SPDX identifiers

As original license mentioned, it is GPL-2.0+ in SPDX.
Then, MODULE_LICENSE() should be "GPL" instead of "GPL v2".
See ${LINUX}/include/linux/module.h

	"GPL"		[GNU Public License v2 or later]
	"GPL v2"	[GNU Public License v2]
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Acked-by: Ramesh Shanmugasundaram <ramesh.shanmugasundaram@bp.renesas.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

drivers/media/platform/rcar_drif.c

+// SPDX-License-Identifier: GPL-2.0+
 /*
  * R-Car Gen3 Digital Radio Interface (DRIF) driver
  *
  * Copyright (C) 2017 Renesas Electronics Corporation
  *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or
- * (at your option) any later version.
- *
  * 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
@@ -1499,5 +1495,5 @@ module_platform_driver(rcar_drif_driver);
 
 MODULE_DESCRIPTION("Renesas R-Car Gen3 DRIF driver");
 MODULE_ALIAS("platform:" RCAR_DRIF_DRV_NAME);
-MODULE_LICENSE("GPL v2");
+MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Ramesh Shanmugasundaram <ramesh.shanmugasundaram@bp.renesas.com>");