Dual-license IBM code contributions

It was brought to our attention that U-Boot contains code derived from the
IBM OpenBIOS source code originally provided with some of the older PowerPC
4xx development boards.  As a result, the original license of this code has
been carried in the various files for a number of years in the U-Boot project.

IBM is dual-licensing the IBM code contributions already present in U-Boot
under either the terms of the GNU General Public License version 2, or the
original code license already present.

Signed-off-by: Josh Boyer <jwboyer@linux.vnet.ibm.com>
diff --git a/cpu/ppc4xx/start.S b/cpu/ppc4xx/start.S
index 60756c3..f967d84 100644
--- a/cpu/ppc4xx/start.S
+++ b/cpu/ppc4xx/start.S
@@ -25,6 +25,8 @@
  * MA 02111-1307 USA
  */
 /*------------------------------------------------------------------------------+
+ *   This source code is dual-licensed.  You may use it under the terms of the
+ *   GNU General Public License version 2, or under the license below.
  *
  *	 This source code has been made available to you by IBM on an AS-IS
  *	 basis.	 Anyone receiving this source is licensed under IBM