qcam: Support Qt versions earlier than 5.9

The QtEventDispatcher timers implementation depends on Qt 5.9 or newer
due to the use of QObject::startTimer(std::chrono::milliseconds).
Support earlier Qt versions by using the QObject::startTimer(int)
version instead.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>

src/qcam/qt_event_dispatcher.cpp

@@ -117,7 +117,7 @@ void QtEventDispatcher::registerTimer(Timer *timer)
 	std::chrono::steady_clock::duration duration = timer->deadline() - now;
 	std::chrono::milliseconds msec =
 		std::chrono::duration_cast<std::chrono::milliseconds>(duration);
-	int timerId = startTimer(msec);
+	int timerId = startTimer(msec.count());
 	timers_[timerId] = timer;
 	timerIds_[timer] = timerId;
 }