[media] dvb_frontend: implement suspend / resume

Move initial suspend / resume support from dvb_usb_v2 to dvb_frontend
as it is dvb general feature that could be used all dvb devices.

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