ret is an "internal" path, no need to re-process it

Where "internal" means that it uses Qt's separator '/', regardless of
the native one.
(cherry picked from commit d4aa1777389f41da60a862a8c371d13839938d43)

Change-Id: Ic23ba0b360020b2e910b1256b38522db5c57f49b
Reviewed-by: João Abecasis <joao.abecasis@nokia.com>

src/corelib/io/qfilesystemengine_win.cpp

@@ -532,7 +532,7 @@ QFileSystemEntry QFileSystemEngine::absoluteName(const QFileSystemEntry &entry)
         // Force uppercase drive letters.
         ret[0] = ret.at(0).toUpper();
     }
-    return QFileSystemEntry(ret);
+    return QFileSystemEntry(ret, QFileSystemEntry::FromInternalPath());
 }
 
 //static