include/fsl_usb.h: Cleanup license header

Replace license header with SPDX license identifier.
Replace GPL-2.0 with GPL-2.0+.

Signed-off-by: York Sun <yorksun@freescale.com>
Acked-by: Ramneek Mehresh <ramneek.mehresh@freescale.com>

include/fsl_usb.h

@@ -3,23 +3,7 @@
  *
  * Copyright 2013 Freescale Semiconductor, Inc.
  *
- * This software may be used and distributed according to the
- * terms of the GNU Public License, Version 2, incorporated
- * herein by reference.
- *
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public License
- * Version 2 as published by the Free Software Foundation.
- *
- * 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
+ * SPDX-License-Identifier:	GPL-2.0+
  */
 
 #ifndef _ASM_FSL_USB_H_