[media] dvb-core: fix return code checking for devices with CA

The test for the return code was mistakenly inverted. This caused DVB
devices with CA module to fail on modprobe.

Tested with TechnoTrend CT2-4650 CI USB tuner.

Signed-off-by: Olli Salonen <olli.salonen@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>