[media] atbm8830: convert set_fontend to new way and fix delivery system

This is one of the cases where the frontend changes is required:
while this device lies to applications that it is a DVB-T, it is,
in fact, a frontend for CTTB delivery system. So, the information
provided for a DVBv3 application should be different than the one
provided to a DVBv5 application.

So, fill delsys with the CTTB delivery system, and use the new
way. there aren't many changes here, as everything on this driver
is on auto mode, probably because of the lack of a proper API
for this delivery system.

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