PM / wakeup: fix kerneldoc comment for pm_wakeup_dev_event()

This brings the kernel doc in line with the function signature.

Signed-off-by: Yangtao Li <tiny.windzz@gmail.com>
Acked-by: Pavel Machek <pavel@ucw.cz>
[ rjw: Subject ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>