ipmi: Add or fix SPDX-License-Identifier in all files

And get rid of the license text that is no longer necessary.

Signed-off-by: Corey Minyard <cminyard@mvista.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Alistair Popple <alistair@popple.id.au>
Cc: Jeremy Kerr <jk@ozlabs.org>
Cc: Joel Stanley <joel@jms.id.au>
Cc: Rocky Craig <rocky.craig@hp.com>

include/linux/ipmi-fru.h

@@ -1,9 +1,8 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
 /*
  * Copyright (C) 2012 CERN (www.cern.ch)
  * Author: Alessandro Rubini <rubini@gnudd.com>
  *
- * Released according to the GNU GPL, version 2 or any later version.
- *
  * This work is part of the White Rabbit project, a research effort led
  * by CERN, the European Institute for Nuclear Research.
  */