[media] cxd2820r: sleep on DVB-T/T2 delivery system switch

Fix bug introduced by multi-frontend to single-frontend change.
It is safer to put DVB-T parts sleeping when auto-switching to DVB-T2
and vice versa. That was original behaviour.

Signed-off-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>