Blackberry: Restart camera viewfinder after standby

Listen to the CAMERA_STATUS_POWERUP signal, which is sent
after standby, and trigger a restart of the viewfinder
in this case.

Change-Id: I426f23657844bb270ddfd0e4bfb35880040aa583
Reviewed-by: Thomas McGuire <thomas.mcguire@kdab.com>

src/plugins/blackberry/camera/bbcamerasession.h

@@ -177,6 +177,7 @@ private slots:
     void handleVideoRecordingPaused();
     void handleVideoRecordingResumed();
     void deviceOrientationChanged(int);
+    void handleCameraPowerUp();
 
 private:
     bool openCamera();