[media] lmedm04: Enable dont_poll for TS2020 tuner

Following a change made to TS2020 tuner in patches
ts2020: Provide DVBv5 API signal strength
ts2020: Allow stats polling to be suppressed

Polling on the driver must be suppressed because
the demuxer is stopped by I2C messages.

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