QTemporaryFileEngine: minor optimization

The original code updated d->fileEntry twice in a row: it assigned to it
directly, then called QFSFileEngine::setFileName() which assigned to
d->fileEntry again. Now only one QFileSystemEntry is constructed.

Change-Id: I3cdc131b97455c14e5b032fbdecdae0eaa32925f
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@gmx.de>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/io/qtemporaryfile_p.h

@@ -88,8 +88,7 @@ public:
         if (filePathIsTemplate) {
             d->fileEntry.clear();
         } else {
-            d->fileEntry = QFileSystemEntry(file);
-            QFSFileEngine::setFileName(file);
+            QFSFileEngine::setFileEntry(QFileSystemEntry(file));
         }
     }
     ~QTemporaryFileEngine();