[media] dvb_frontend: Fix DVBv3 emulation

For frontends with ISDB-T, DVB-T2, CMDBTH, etc, some code is
needed, in order to provide emulation. Add such code, and check
if the desired delivery system is supported by the frontend.

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