Reverse the flush-screen-context test

It was backwards so the screen context was being flushed on every screen
interaction when the parameter was _not_ specified.  During mouse/touch
movement, the number of flushes can be so great that it negatively
impacts performance.

Change-Id: I4dfe9c33c8ce31237db1d78db1cb8e04c00c4dd3
Reviewed-by: Dan Cape <dcape@qnx.com>
Reviewed-by: Rafael Roquetto <rafael.roquetto@kdab.com>

src/plugins/platforms/qnx/qqnxintegration.cpp

@@ -116,7 +116,7 @@ static inline QQnxIntegration::Options parseOptions(const QStringList &paramList
         options |= QQnxIntegration::FullScreenApplication;
     }
 
-    if (!paramList.contains(QLatin1String("flush-screen-context"))) {
+    if (paramList.contains(QLatin1String("flush-screen-context"))) {
         options |= QQnxIntegration::AlwaysFlushScreenContext;
     }