schema mount UPDATE support for creating nested data

Not just parsing it directly.
diff --git a/src/validation.c b/src/validation.c
index 8004b44..c2c33d4 100644
--- a/src/validation.c
+++ b/src/validation.c
@@ -279,7 +279,7 @@
             LY_CHECK_RET(ret);
 
             /* remove this item from the set */
-            ly_set_rm_index(node_types, i, free);
+            ly_set_rm_index(ext_val, i, free);
         } while (i);
     }