[media] docs-rst: Convert DVB uAPI to use C function references

Name all ioctl references and make them match the ioctls that
are documented. That will improve the cross-reference index,
as it will have all ioctls and syscalls there.

While here, improve the documentation, marking the deprecated
ioctls, and making the non-deprecated ones more like the rest
of the media book.

Also, add a notice for ioctls that still require documentation.

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