doc-rst: linux_tv: use references for structures

doc-rst: linux_tv: use references for structures

On several places, instead of using references, the code was
using some other tag. Not sure if this was due to the conversion,
or if something were already wrong on the DocBook. In any case,
let's fix them.

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>