rtc: omap: convert to SPDX identifier

Use SPDX-License-Identifier instead of a verbose license text.
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

drivers/rtc/rtc-omap.c

+// SPDX-License-Identifier: GPL-2.0+
 /*
  * TI OMAP Real Time Clock interface for Linux
  *
@@ -6,11 +7,6 @@
  *
  * Copyright (C) 2006 David Brownell (new RTC framework)
  * Copyright (C) 2014 Johan Hovold <johan@kernel.org>
- *
- * 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.
  */
 
 #include <dt-bindings/gpio/gpio.h>