hwrng: bcm2835 - Switch to SPDX identifier

Adopt the SPDX license identifier headers to ease license compliance
management. While we are at this fix the comment style, too.

Cc: Lubomir Rintel <lkundrak@v3.sk>
Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Eric Anholt <eric@anholt.net>
Acked-by: Lubomir Rintel <lkundrak@v3.sk>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/char/hw_random/bcm2835-rng.c

-/**
+// SPDX-License-Identifier: GPL-2.0
+/*
  * Copyright (c) 2010-2012 Broadcom. All rights reserved.
  * Copyright (c) 2013 Lubomir Rintel
- *
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public License ("GPL")
- * version 2, as published by the Free Software Foundation.
  */
 
 #include <linux/hw_random.h>