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