AP_Param: simplify set_defaults_from_table error path

libraries/AP_Param/AP_Param.cpp

@@ -2486,10 +2486,7 @@ void AP_Param::set_defaults_from_table(const struct defaults_table_struct *table
 {
     for (uint8_t i=0; i<count; i++) {
         if (!AP_Param::set_default_by_name(table[i].name, table[i].value)) {
-            char *buf = nullptr;
-            if (asprintf(&buf, "param deflt fail:%s", table[i].name) > 0) {
-                AP_BoardConfig::config_error("%s", buf);
-            }
+            AP_BoardConfig::config_error("param deflt fail:%s", table[i].name);
         }
     }
 }