Unify the duplicated timekeeping handling code of low and high res tick
sched handlers.
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>