time: Remove nonexistent function prototype

The function clocksource_get_next() was removed in commit 75c5158f70
(timekeeping: Update clocksource with stop_machine), but the
prototype was not removed with it. Remove the prototype.

Signed-off-by: Yingjoe Chen <yingjoe.chen@mediatek.com>
Cc: <linux-arm-kernel@lists.infradead.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: <srv_heupstream@mediatek.com>
Cc: John Stultz <john.stultz@linaro.org>
Link: http://lkml.kernel.org/r/1428674150-1780-1-git-send-email-yingjoe.chen@mediatek.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

include/linux/clocksource.h

@@ -181,7 +181,6 @@ static inline s64 clocksource_cyc2ns(cycle_t cycles, u32 mult, u32 shift)
 
 extern int clocksource_unregister(struct clocksource*);
 extern void clocksource_touch_watchdog(void);
-extern struct clocksource* clocksource_get_next(void);
 extern void clocksource_change_rating(struct clocksource *cs, int rating);
 extern void clocksource_suspend(void);
 extern void clocksource_resume(void);