PM: dpm_watchdog: Add sysctl interface for DPM watchdog timeouts

PM: dpm_watchdog: Add sysctl interface for DPM watchdog timeouts

Introduce sysctl knobs to allow configuring DPM watchdog timeouts at
runtime.

Currently, these timeouts are fixed at compile time via
CONFIG_DPM_WATCHDOG_TIMEOUT and CONFIG_DPM_WATCHDOG_WARNING_TIMEOUT.
This limits flexibility if the timeouts need to be adjusted for
different testing scenarios or hardware behaviors without rebuilding
the kernel.

Add the following sysctl files under /proc/sys/kernel/:

 - dpm_watchdog_timeout_secs: The total timeout before panic. The
   maximum value is capped at CONFIG_DPM_WATCHDOG_TIMEOUT to prevent
   unreasonably large timeouts.

 - dpm_watchdog_warning_timeout_secs: The warning timeout. The maximum
   value is capped at the current dpm_watchdog_timeout_secs.

Both sysctls have a minimum value of 1.

Signed-off-by: Tzung-Bi Shih <tzungbi@kernel.org>
Link: https://patch.msgid.link/20260608021526.1023248-4-tzungbi@kernel.org
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>