Add GPL-2.0+ SPDX-License-Identifier to source files

Signed-off-by: Wolfgang Denk <wd@denx.de>
[trini: Fixup common/cmd_io.c]
Signed-off-by: Tom Rini <trini@ti.com>
diff --git a/drivers/net/e1000.c b/drivers/net/e1000.c
index c1863f4..57aa53d 100644
--- a/drivers/net/e1000.c
+++ b/drivers/net/e1000.c
@@ -9,22 +9,7 @@
 
   Copyright(c) 1999 - 2002 Intel Corporation. All rights reserved.
 
-  This program is free software; you can redistribute it and/or modify it
-  under the terms of the GNU General Public License as published by the Free
-  Software Foundation; either version 2 of the License, or (at your option)
-  any later version.
-
-  This program is distributed in the hope that it will be useful, but WITHOUT
-  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
-  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
-  more details.
-
-  You should have received a copy of the GNU General Public License along with
-  this program; if not, write to the Free Software Foundation, Inc., 59
-  Temple Place - Suite 330, Boston, MA	02111-1307, USA.
-
-  The full GNU General Public License is included in this distribution in the
-  file called LICENSE.
+ * SPDX-License-Identifier:	GPL-2.0+
 
   Contact Information:
   Linux NICS <linux.nics@intel.com>