validation BUGFIX validate only specific module subtrees

Refs sysrepo/sysrepo#2437
diff --git a/src/validation.c b/src/validation.c
index 6b2c841..e916930 100644
--- a/src/validation.c
+++ b/src/validation.c
@@ -1498,6 +1498,10 @@
         if (validate_subtree) {
             /* process nested nodes */
             LY_LIST_FOR(*first2, iter) {
+                if (lyd_owner_module(iter) != mod) {
+                    break;
+                }
+
                 ret = lyd_validate_subtree(iter, node_when_p, node_exts_p, node_types_p, meta_types_p,
                         (val_opts & LYD_VALIDATE_NO_STATE) ? LYD_IMPLICIT_NO_STATE : 0, diff);
                 LY_CHECK_GOTO(ret, cleanup);