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/board/karo/tk71/kwbimage.cfg b/board/karo/tk71/kwbimage.cfg
index 9a9cf9d..a32e27c 100644
--- a/board/karo/tk71/kwbimage.cfg
+++ b/board/karo/tk71/kwbimage.cfg
@@ -6,23 +6,7 @@
 # adopted to TK71 by
 # Nils Faerber <nils.faerber@kernelconcepts.de>
 #
-# See file CREDITS for list of people who contributed to this
-# project.
-#
-# 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., 51 Franklin Street, Fifth Floor, Boston,
-# MA 02110-1301 USA
+# SPDX-License-Identifier:	GPL-2.0+
 #
 # Refer doc/README.kwbimage for more details about how-to configure
 # and create kirkwood boot image