[media] flexcop: handle errors from dvb_net_init

Bail out if dvb_net_init encounters an error (for example an
out-of-memory condition), now that it reports them.

[mchehab@redhat.com: CodingStyle fix: don't use  "if ((ret = foo()) < 0)"]
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>