kconfig: explicitly introduce expression list

Rename E_CHOICE to E_LIST to explicitly add support for expression
lists. Add a helper macro expr_list_for_each_sym to more easily iterate
over the list.

Signed-off-by: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
diff --git a/scripts/kconfig/menu.c b/scripts/kconfig/menu.c
index e9deebe..3637d10 100644
--- a/scripts/kconfig/menu.c
+++ b/scripts/kconfig/menu.c
@@ -331,7 +331,7 @@
 			prop = sym_get_choice_prop(sym);
 			for (ep = &prop->expr; *ep; ep = &(*ep)->left.expr)
 				;
-			*ep = expr_alloc_one(E_CHOICE, NULL);
+			*ep = expr_alloc_one(E_LIST, NULL);
 			(*ep)->right.sym = menu->sym;
 		}
 		if (menu->list && (!menu->prompt || !menu->prompt->text)) {