in_syslog: add desc to message_length_limit

lib/fluent/plugin/in_syslog.rb

@@ -85,15 +85,16 @@ class SyslogInput < Input
     config_param :source_hostname_key, :string, default: nil
     desc 'The field name of source address of sender.'
     config_param :source_address_key, :string, default: nil
-
     desc 'The field name of the priority.'
     config_param :priority_key, :string, default: nil
     desc 'The field name of the facility.'
     config_param :facility_key, :string, default: nil
 
-    config_param :blocking_timeout, :time, default: 0.5
+    desc "The max bytes of message"
     config_param :message_length_limit, :size, default: 2048
 
+    config_param :blocking_timeout, :time, default: 0.5
+
     config_section :parse do
       config_set_default :@type, DEFAULT_PARSER
       config_param :with_priority, :bool, default: true