[media] DocBook: improve documentation of the properties structs

Rename the tytle of the struct documentation to reflect
the name of the structures, and use links to do cross-ref.

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

diff --cc Documentation/DocBook/media/dvb/dvbproperty.xml
Simple merge

diff --cc Documentation/DocBook/media/dvb/fe-get-property.xml
Simple merge