media: wl128x: Fix an error code in fm_download_firmware()

commit ef4bb63d upstream.

We forgot to set "ret" on this error path.

Fixes: e8454ff7 ("[media] drivers:media:radio: wl128x: FM Driver Common sources")

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>