ntp: Remove tickadj

There are zero users of tickadj. So remove it.

Signed-off-by: John Stultz <johnstul@us.ibm.com>
LKML-Reference: <1268968769-19209-2-git-send-email-johnstul@us.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>