kconfig: add a function to dump all menu entries in a tree-like format

This is useful for debugging purposes. menu_finalize() re-parents menu
entries, and this function can be used to dump the final structure of
the menu tree.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

scripts/kconfig/lkc.h

@@ -102,6 +102,7 @@ struct menu *menu_get_menu_or_parent_menu(struct menu *menu);
 int get_jump_key_char(void);
 struct gstr get_relations_str(struct symbol **sym_arr, struct list_head *head);
 void menu_get_ext_help(struct menu *menu, struct gstr *help);
+void menu_dump(void);
 
 /* symbol.c */
 void sym_clear_all_valid(void);