Revert "build: scripts/config - update to kconfig-v5.6"

This reverts commit dcf3e63a35.

The kconfig update requires further testing and refinement until it can
remain in tree. Main problems are:

 - Recursive deps are now fatal instead of a warning
 - Previously legal syntax now leads to hard failures
 - It fails all package builds since multiple days

The updated kconfig implementation needs to cope with the current status
quo in the various package feeds before we can reconsider it for master.

It is not desirable that single broken packages can hard-fail the entire
build pipeline.

Signed-off-by: Jo-Philipp Wich <jo@mein.io>

scripts/config/qconf.h

@@ -1,6 +1,6 @@
-/* SPDX-License-Identifier: GPL-2.0 */
 /*
  * Copyright (C) 2002 Roman Zippel <zippel@linux-m68k.org>
+ * Released under the terms of the GNU GPL v2.0.
  */
 
 #include <QTextBrowser>
@@ -291,7 +291,6 @@ protected:
 class ConfigMainWindow : public QMainWindow {
 	Q_OBJECT
 
-	char *configname;
 	static QAction *saveAction;
 	static void conf_changed(void);
 public: