sh: boards: convert to SPDX identifiers

Update license to use SPDX-License-Identifier instead of verbose license
text.

Link: http://lkml.kernel.org/r/87in08ct0n.wl-kuninori.morimoto.gx@renesas.com
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Cc: Rich Felker <dalias@libc.org>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/sh/boards/mach-dreamcast/irq.c

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0
 /*
  * arch/sh/boards/dreamcast/irq.c
  *
@@ -6,7 +7,6 @@
  * Copyright (c) 2001, 2002 M. R. Brown <mrbrown@0xd6.org>
  *
  * This file is part of the LinuxDC project (www.linuxdc.org)
- * Released under the terms of the GNU GPL v2.0
  */
 #include <linux/irq.h>
 #include <linux/io.h>