Documentation: PM: *_autosuspend() functions update last busy time

Document that the *_autosuspend() variants of the Runtime PM functions
update the last busy timestamp.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Link: https://patch.msgid.link/20250616061212.2286741-7-sakari.ailus@linux.intel.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Author: Sakari Ailus

Documentation/power/runtime_pm.rst

@@ -887,7 +887,8 @@ instead of the non-autosuspend counterparts::
 
 Drivers may also continue to use the non-autosuspend helper functions; they
 will behave normally, which means sometimes taking the autosuspend delay into
-account (see pm_runtime_idle).
+account (see pm_runtime_idle). The autosuspend variants of the functions also
+call pm_runtime_mark_last_busy().
 
 Under some circumstances a driver or subsystem may want to prevent a device
 from autosuspending immediately, even though the usage counter is zero and the