adapt to the coop-by-default syntax in our port

Index: mono/utils/mono-threads-coop.c
--- mono/utils/mono-threads-coop.c.orig
+++ mono/utils/mono-threads-coop.c
@@ -580,7 +580,7 @@ mono_threads_assert_gc_unsafe_region (void)
 static int
 threads_suspend_policy_default (void)
 {
-#if defined (ENABLE_COOP_SUSPEND)
+#if !defined (DISABLE_COOP_SUSPEND)
 	return MONO_THREADS_SUSPEND_FULL_COOP;
 #elif defined (ENABLE_HYBRID_SUSPEND)
 	return MONO_THREADS_SUSPEND_HYBRID;