Kconfig: remove unused function 'menu_get_root_menu'

There is nowhere calling `menu_get_root_menu` function,
so remove it.
Signed-off-by: Zeng Heng <zengheng4@huawei.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

scripts/kconfig/lkc.h

@@ -98,7 +98,6 @@ bool menu_is_empty(struct menu *menu);
 bool menu_is_visible(struct menu *menu);
 bool menu_has_prompt(struct menu *menu);
 const char *menu_get_prompt(struct menu *menu);
-struct menu *menu_get_root_menu(struct menu *menu);
 struct menu *menu_get_parent_menu(struct menu *menu);
 bool menu_has_help(struct menu *menu);
 const char *menu_get_help(struct menu *menu);

scripts/kconfig/menu.c

@@ -661,11 +661,6 @@ const char *menu_get_prompt(struct menu *menu)
 	return NULL;
 }
 
-struct menu *menu_get_root_menu(struct menu *menu)
-{
-	return &rootmenu;
-}
-
 struct menu *menu_get_parent_menu(struct menu *menu)
 {
 	enum prop_type type;