QFSFileEnginePrivate::map: flags is not unused

It's used below:
    if (flags & QFileDevice::MapPrivateOption) {
        sharemode = MAP_PRIVATE;
        access |= PROT_WRITE;
    }

Change-Id: I8d96dea9955d4c749b99fffd14cd5222762699d4
Reviewed-by: Robin Burchell <robin.burchell@crimson.no>

src/corelib/io/qfsfileengine_unix.cpp

@@ -725,7 +725,6 @@ uchar *QFSFileEnginePrivate::map(qint64 offset, qint64 size, QFile::MemoryMapFla
 #endif
 
     Q_Q(QFSFileEngine);
-    Q_UNUSED(flags);
     if (openMode == QIODevice::NotOpen) {
         q->setError(QFile::PermissionsError, qt_error_string(int(EACCES)));
         return 0;