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/xpath.h b/src/xpath.h
index 8224dfe..4da73ad 100644
--- a/src/xpath.h
+++ b/src/xpath.h
@@ -264,7 +264,7 @@
     const struct lysc_node *context_op;
     const struct lyd_node *tree;
     const struct lys_module *cur_mod;
-    LY_PREFIX_FORMAT format;
+    LY_VALUE_FORMAT format;
     void *prefix_data;
 };
 
@@ -295,7 +295,7 @@
  * @return LY_EINVAL, LY_EMEM, LY_EINT for other errors.
  */
 LY_ERR lyxp_eval(const struct ly_ctx *ctx, const struct lyxp_expr *exp, const struct lys_module *cur_mod,
-        LY_PREFIX_FORMAT format, void *prefix_data, const struct lyd_node *ctx_node, const struct lyd_node *tree,
+        LY_VALUE_FORMAT format, void *prefix_data, const struct lyd_node *ctx_node, const struct lyd_node *tree,
         struct lyxp_set *set, uint32_t options);
 
 /**
@@ -312,7 +312,7 @@
  * @return LY_ERR (same as ::lyxp_eval()).
  */
 LY_ERR lyxp_atomize(const struct ly_ctx *ctx, const struct lyxp_expr *exp, const struct lys_module *cur_mod,
-        LY_PREFIX_FORMAT format, void *prefix_data, const struct lysc_node *ctx_scnode, struct lyxp_set *set,
+        LY_VALUE_FORMAT format, void *prefix_data, const struct lysc_node *ctx_scnode, struct lyxp_set *set,
         uint32_t options);
 
 /* used only internally, maps with @ref findxpathoptions */