libyang REFACTOR rename LY_PREFIX_FORMAT values

Reflect that the value format is the primary concern of the enum, the prefix
interpretation is only based on the format.
diff --git a/src/printer_tree.c b/src/printer_tree.c
index df389cd..286b286 100644
--- a/src/printer_tree.c
+++ b/src/printer_tree.c
@@ -3714,7 +3714,7 @@
 
     ly_parse_nodeid(&id, &prefix, &prefix_len, &name, &name_len);
     if (prefix) {
-        mod = ly_resolve_prefix(pmod->mod->ctx, prefix, prefix_len, LY_PREF_SCHEMA, pmod);
+        mod = ly_resolve_prefix(pmod->mod->ctx, prefix, prefix_len, LY_VALUE_SCHEMA, pmod);
         ret = mod->parsed == pmod;
     } else {
         ret = 1;