Skew tick for systems with a large number of processors

Skew tick for systems with a large number of processors

Synchronized ticks mean that all processors will simultaneously process
ticks and enter the scheduler. So the contention increases as the number
of cpu increases. The contention causes latency jitter that scales with
the number of processors.

Staggering the timer interrupt also helps mitigate voltage droop related
issues that may be observed in SOCs with large core counts.
See https://semiengineering.com/mitigating-voltage-droop/ for a more
detailed explanation.

Switch to skewed tick for systems with more than 64 processors.

Signed-off-by: Christoph Lameter (Ampere) <cl@gentwo.org>