media: dvbsky: Remove duplicate error reporting for dvbsky_usb_generic_rw

Errors are already reported by the common code in dvb_usb_v2_generic_io
(which dvbsky_usb_generic_rw is a wrapper of), so there is no reason
report the error again.

Signed-off-by: Stefan Brüns <stefan.bruens@rwth-aachen.de>
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>