watchdog/perf: Provide function for adjusting the event period

watchdog/perf: Provide function for adjusting the event period

Architecture's using perf events for hard lockup detection needs to
convert the watchdog_thresh to the event's period, some architecture
for example arm64 perform this conversion using the CPU's maximum
frequency which will be acquired by cpufreq. However by the time
the lockup detector's initialized the cpufreq driver may not be
initialized, thus launch a watchdog with inaccurate period. Provide
a function hardlockup_detector_perf_adjust_period() to allowing
adjust the event period. Then architecture can update with more
accurate period if cpufreq is initialized.

Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Yicong Yang <yangyicong@hisilicon.com>
Link: https://lore.kernel.org/r/20250701110214.27242-2-yangyicong@huawei.com
Signed-off-by: Will Deacon <will@kernel.org>