doc: improve rinfo object documentation

Provide details for fields of rinfo object of UDP message event.

PR-URL: https://github.com/nodejs/node/pull/10050
Reviewed-By: James M Snell <jasnell@gmail.com>

doc/api/dgram.md

@@ -70,20 +70,14 @@ datagram messages. This occurs as soon as UDP sockets are created.
 added: v0.1.99
 -->
 
+The `'message'` event is emitted when a new datagram is available on a socket.
+The event handler function is passed two arguments: `msg` and `rinfo`.
 * `msg` {Buffer} - The message
 * `rinfo` {Object} - Remote address information
-
+  * `address` {String} The sender address
-The `'message'` event is emitted when a new datagram is available on a socket.
+  * `family` {String} The address family (`'IPv4'` or `'IPv6'`)
-The event handler function is passed two arguments: `msg` and `rinfo`. The
+  * `port` {Number} The sender port
-`msg` argument is a [`Buffer`][] and `rinfo` is an object with the sender's
+  * `size` {Number} The message size
-address information provided by the `address`, `family` and `port` properties:
-
-```js
-socket.on('message', (msg, rinfo) => {
-  console.log('Received %d bytes from %s:%d\n',
-              msg.length, rinfo.address, rinfo.port);
-});
-```
 
 ### socket.addMembership(multicastAddress[, multicastInterface])
 <!-- YAML