If you deploy any of the three mobile configuration types and they are deployed appropriately, you do not need a mobile XML sitemap file.
Google's John Mueller said you should NOT have a mobile sitemap for mobile sites. The only case you should have a separate mobile site is when you have a feature phone (WAP/WML, etc) version of your site, which is something most people don't bother with these days.
But for an ordinary mobile-friendly website, no new sitemap is needed or wanted. It can cause more confusion if you add a mobile sitemap file.
