Support all known DPI values

Extend the dpi range to complete the table, as you can see here xxhdpi goes from 480 to 639 than becomes xxxhdpi at 640
http://developer.android.com/guide/practices/screens_support.html
Support the devices that use xxxhdpi (e.g LG G3) or people who use a modified DPI higher than 480 in build.prop to get rid of the "unknown" value being returned

Change-Id: I697f917e1e16e0e097200eaebab25e69cce8a3b7