hrtimer: Annotate hrtimer_cpu_base_.*_expiry() for sparse.

The two hrtimer_cpu_base_.*_expiry() functions are wrappers around the
locking functions and sparse complains about the missing counterpart.

Add sparse annotation to denote that this bevaviour is expected.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20240812105326.2240000-3-bigeasy@linutronix.de