[media] dvb-core: allow demods to specify the supported delsys

[media] dvb-core: allow demods to specify the supported delsys

The dvb were originally written for DVB-T/C/S and ATSC. So,
the original frontend struct has fields to describe only those three
standards.

While 2nd gen standards are similar to these, new standards
like DSS, ISDB and CTTB don't fit on any of the above types.

While there's a way for the drivers to explicitly change whatever
default DELSYS were filled inside the core, still a fake value is
needed there, and a "compat" code to allow DVBv3 applications to
work with those delivery systems is needed. This is good for a
short term solution, while applications aren't using DVBv5 directly.

However, at long term, this is bad, as the compat code runs even
if the application is using DVBv5. Also, the compat code is not
perfect, and only works when the frontend is capable of auto-detecting
the parameters that aren't visible by the faked delivery systems.

So, let the frontend fill the supported delivery systems at the
device properties directly.

The future plan is that the drivers will stop filling ops->info.type,
filling, instead, ops->delsys. This will allow multi-frontend
devices like drx-k to use just one frontend structure for all supported
delivery systems.

Of course, the core will keep using it, in order to keep allowing
DVBv3 calls.

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