ntp: Remove duplicated include

Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: <john.stultz@linaro.org>
Cc: <sboyd@kernel.org>
Link: https://lkml.kernel.org/r/20181209062225.4344-1-yuehaibing@huawei.com

kernel/time/ntp.c

@@ -17,7 +17,6 @@
 #include <linux/mm.h>
 #include <linux/module.h>
 #include <linux/rtc.h>
-#include <linux/math64.h>
 
 #include "ntp_internal.h"
 #include "timekeeping_internal.h"