[media] gspca - cpia1: Fix error check

It looks to me like it was intended to check the return value
at this point.

Signed-off-by: Nicolas Kaiser <nikai@nikai.net>
Signed-off-by: Jean-François Moine <moinejf@free.fr>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>