[media] PCTV290E: Attach a single frontend

PCTV290E: Attach a single frontend, rather than a frontend each per
delivery system, whereby a multistandard frontend can advertise all
associated delivery systems.

Signed-off-by: Manu Abraham <abraham.manu@gmail.com>
Acked-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>