time/jiffies: Register jiffies clocksource before usage

In the Linux kernel, the following vulnerability has been resolved: time/jiffies: Register jiffies clocksource before usage Teddy reported that a XEN HVM has a long boot delay, which was bisected to the recent enhancements to the negative motion detection. It turned out that the jiffies clocksource is used in early boot before it is registered, which leaves the max_delta_raw field at zero. That causes the read out to be clamped to the max delta of 0, which means time is not making progress. Cure it by ensuring that it is initialized before its first usage in timekeeping_init().