tick: Remove unnused tick_nohz_get_idle_calls()

The function returns the idle calls counter for the current cpu and
therefore usually isn't what the caller wants. It is unnused since
commit 466a2b42 ("cpufreq: schedutil: Use idle_calls counter of the
remote CPU")

Signed-off-by: Christian Loehle <christian.loehle@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20240617161615.49309-1-christian.loehle@arm.com