tick-sched: Fix function names in comments

When referencing functions in comments, it might be helpful to use full
function names (including the prefix) to be able to find it when grepping.

Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/r/20231201092654.34614-2-anna-maria@linutronix.de