[media] ts2020: Allow stats polling to be suppressed

Statistics polling can not be done by lmedm04 driver's implementation of
M88RS2000/TS2020 because I2C messages stop the device's demuxer, so allow
polling for statistics to be suppressed in the ts2020 driver by setting
dont_poll in the ts2020_config struct.

Reported-by: Malcolm Priestley <tvboxspy@gmail.com>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Malcolm Priestley <tvboxspy@gmail.com>
Signed-off-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>