clocksource/drivers/mxs_timer: Switch to SPDX identifier

Adopt the SPDX license identifier headers to ease license compliance
management.
Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>

drivers/clocksource/mxs_timer.c

-/*
- *  Copyright (C) 2000-2001 Deep Blue Solutions
- *  Copyright (C) 2002 Shane Nay (shane@minirl.com)
- *  Copyright (C) 2006-2007 Pavel Pisa (ppisa@pikron.com)
- *  Copyright (C) 2008 Juergen Beisert (kernel@pengutronix.de)
- *  Copyright (C) 2010 Freescale Semiconductor, Inc. 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., 51 Franklin Street, Fifth Floor, Boston,
- * MA 02110-1301, USA.
- */
+// SPDX-License-Identifier: GPL-2.0+
+//
+//  Copyright (C) 2000-2001 Deep Blue Solutions
+//  Copyright (C) 2002 Shane Nay (shane@minirl.com)
+//  Copyright (C) 2006-2007 Pavel Pisa (ppisa@pikron.com)
+//  Copyright (C) 2008 Juergen Beisert (kernel@pengutronix.de)
+//  Copyright (C) 2010 Freescale Semiconductor, Inc. All Rights Reserved.
 
 #include <linux/err.h>
 #include <linux/interrupt.h>