drm: dw-hdmi-i2s: convert to SPDX identifiers

This patch updates license to use SPDX-License-Identifier
instead of verbose license text.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Link: https://patchwork.freedesktop.org/patch/msgid/87lg4n1izg.wl-kuninori.morimoto.gx@renesas.com

drivers/gpu/drm/bridge/synopsys/dw-hdmi-i2s-audio.c

+// SPDX-License-Identifier: GPL-2.0
 /*
  * dw-hdmi-i2s-audio.c
  *
  * Copyright (c) 2017 Renesas Solutions Corp.
  * Kuninori Morimoto <kuninori.morimoto.gx@renesas.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 <drm/bridge/dw_hdmi.h>