media: docs: uAPI: dvb/video: completing the documentation (data types)

The existing documentation of the legacy DVB Decoder API was incomplete.

Revising the documentation, adding missing parts and arranging the
documentation files new.

This patch contains the documentation of the data types defined in
video.h.

Link: https://lore.kernel.org/linux-media/20240128233249.32794-6-herdler@nurfuerspam.de


Signed-off-by: Stefan Herdler <herdler@nurfuerspam.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>