clocksource/drivers/jcore: Convert to SPDX identifier

The licensing text references explicitely the COPYING file in the kernel
base directory, which is clearly GPL version 2 only.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Rich Felker <dalias@libc.org>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20220510171254.467236056@linutronix.deSigned-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>

drivers/clocksource/jcore-pit.c

+// SPDX-License-Identifier: GPL-2.0
 /*
  * J-Core SoC PIT/clocksource driver
  *
  * Copyright (C) 2015-2016 Smart Energy Instruments, Inc.
- *
- * This file is subject to the terms and conditions of the GNU General Public
- * License.  See the file "COPYING" in the main directory of this archive
- * for more details.
  */
 
 #include <linux/kernel.h>