[Ada] Fix crash on quantified expression in expression function (2)

[Pierre-Marie de Rodat]

This just replaces Find_Aspect with Find_Value_Of_Aspect, which seems
to be the preferred idiom to retrieve the value of an aspect.

Tested on x86_64-pc-linux-gnu, committed on trunk

gcc/ada/

        * freeze.adb (Freeze_Expr_Types): Replace call to Find_Aspect
        with call to Find_Value_Of_Aspect and adjust accordingly.
diff --git a/gcc/ada/freeze.adb b/gcc/ada/freeze.adb
--- a/gcc/ada/freeze.adb
+++ b/gcc/ada/freeze.adb
@@ -8000,10 +8000,11 @@ package body Freeze is
          then
             declare
                Iter : constant Node_Id :=
-                           Find_Aspect (Etype (Node), Aspect_Default_Iterator);
+                 Find_Value_Of_Aspect (Etype (Node), Aspect_Default_Iterator);
+
             begin
                if Present (Iter) then
-                  Check_And_Freeze_Type (Etype (Expression (Iter)));
+                  Check_And_Freeze_Type (Etype (Iter));
                end if;
             end;
          end if;