hw_random: ixp4xx: Use SPDX license tag

This switches the IXP4xx hardware random driver to use
the SPDX type license tag.

Cc: Deepak Saxena <dsaxena@plexity.net>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/char/hw_random/ixp4xx-rng.c

+// SPDX-License-Identifier: GPL-2.0
 /*
  * drivers/char/hw_random/ixp4xx-rng.c
  *
@@ -8,10 +9,6 @@
  * Copyright 2005 (c) MontaVista Software, Inc.
  *
  * Fixes by Michael Buesch
- *
- * This file is licensed under  the terms of the GNU General Public
- * License version 2. This program is licensed "as is" without any
- * warranty of any kind, whether express or implied.
  */
 
 #include <linux/kernel.h>