imx: fix licensing in i.MX files

Some files for i.MX do not yet have the SPDX ID to reference the correct
license.

Signed-off-by: Stefano Babic <sbabic@denx.de>
Reviewed-by: Wolfgang Denk <wd@denx.de>
diff --git a/arch/arm/include/asm/arch-mxs/iomux-mx23.h b/arch/arm/include/asm/arch-mxs/iomux-mx23.h
index 7cb5e71..690929c 100644
--- a/arch/arm/include/asm/arch-mxs/iomux-mx23.h
+++ b/arch/arm/include/asm/arch-mxs/iomux-mx23.h
@@ -2,12 +2,7 @@
  * Copyright (C) 2009-2010 Amit Kucheria <amit.kucheria@canonical.com>
  * Copyright (C) 2010 Freescale Semiconductor, Inc.
  *
- * The code contained herein is licensed under the GNU General Public
- * License. You may obtain a copy of the GNU General Public License
- * Version 2 or later at the following locations:
- *
- * http://www.opensource.org/licenses/gpl-license.html
- * http://www.gnu.org/copyleft/gpl.html
+ * SPDX-License-Identifier:	GPL-2.0+
  */
 
 #ifndef __MACH_IOMUX_MX23_H__