Fix build error when targeting Blackberry Playbook

The emitSignals() slot is only implemented/used in the file
qqnxfiledialoghelper_bb10.cpp, not in <...>_playbook.cpp.

Change-Id: I068e843be74ec9639d889b87caa016c8506ec905
Reviewed-by: Robin Burchell <robin+qt@viroteck.net>
Reviewed-by: Rafael Roquetto <rafael.roquetto@kdab.com>

src/plugins/platforms/qnx/qqnxfiledialoghelper.h

@@ -88,7 +88,9 @@ Q_SIGNALS:
     void dialogClosed();
 
 private Q_SLOTS:
+#if !defined(Q_OS_BLACKBERRY_TABLET)
     void emitSignals();
+#endif
 
 private:
     void setNameFilter(const QString &filter);