[media] usb: au0828: remove redundant code

The check for ret being non-zero is false as ret is always
zero, hence we have redundant dead code that can be removed.

Detected with CoverityScan, CID#112968 ("Constant' variable guards
dead code (DEADCODE)'")

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>