util/kconfig: Uprev to Linux 6.8's kconfig

Linux kconfig has its own implementation of KCONFIG_WERROR now, so use
that. This reduces our patch count by 2.

Change-Id: I4f5f1f552e96f8ef7a4c5c0ab2ab7e2b6d798ceb
Signed-off-by: Patrick Georgi <patrick@georgi.software>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/81223
Reviewed-by: Felix Singer <service+coreboot-gerrit@felixsinger.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

util/kconfig/mnconf-common.h

@@ -0,0 +1,18 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef MNCONF_COMMON_H
+#define MNCONF_COMMON_H
+
+#include <stddef.h>
+
+struct search_data {
+	struct list_head *head;
+	struct menu *target;
+};
+
+extern int jump_key_char;
+
+int next_jump_key(int key);
+int handle_search_keys(int key, size_t start, size_t end, void *_data);
+int get_jump_key_char(void);
+
+#endif /* MNCONF_COMMON_H */