cam: Move event loop exit from CameraSession to CamApp

Make exiting the event loop the responsibility of the application, not
the camera session, to prepare for support of multiple camera sessions.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

src/cam/camera_session.cpp

@@ -232,7 +232,7 @@ void CameraSession::processRequest(Request *request)
 
 	captureCount_++;
 	if (captureLimit_ && captureCount_ >= captureLimit_) {
-		EventLoop::instance()->exit(0);
+		captureDone.emit();
 		return;
 	}