[media] DocBook: Update DVB supported standards at introduction

The list of standards at the media docbook is incomplete, and it
is mentioning that the DVB-S2 & friends is "currently being updated".
That's wrong, as such update occurred back in 2008.

So, provide a more complete list of supported standards and add
a reference to the actual list.

Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>