[media] dvb: return the error from i2c_transfer if negative

Just returns whatever error that was returned by the i2c core,
in the case of errors, only returning -EREMOTEIO if the transfer size
is not what it was expected.

Signed-off-by: Hans Wennborg <hans@hanshq.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>