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>