Removed deprecated xvba ppa

No longer used see http://forum.xbmc.org/showthread.php?tid=141369&pid=1583833#pid1583833

@bram77 see my branch for updated ppas which were added at 45924868ebf5cd69b838b9fd16e9231375b55cac and later updated at https://github.com/uNiversaI/xbmc-ubuntu-minimal/commit/e7317a8bacb5ca30893634c64335b79869dd82eb

in any case much work is required to get ATI working properly.