[media] drivers/media/radio/radio-cadet.c: fix error return code

Convert a nonnegative error return code to a negative one, as returned
elsewhere in the function.
A simplified version of the semantic match that finds this problem is as
follows: (http://coccinelle.lip6.fr/)
// <smpl>
(
if@p1 (\(ret < 0\|ret != 0\))
 { ... return ret; }
|
ret@p1 = 0
)
... when != ret = e1
    when != &ret
*if(...)
{
  ... when != ret = e2
      when forall
 return ret;
}
// </smpl>

Signed-off-by: Peter Senna Tschudin <peter.senna@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/radio/radio-cadet.c

@@ -645,7 +645,8 @@ static int __init cadet_init(void)
 	set_bit(V4L2_FL_USE_FH_PRIO, &dev->vdev.flags);
 	video_set_drvdata(&dev->vdev, dev);
 
-	if (video_register_device(&dev->vdev, VFL_TYPE_RADIO, radio_nr) < 0)
+	res = video_register_device(&dev->vdev, VFL_TYPE_RADIO, radio_nr);
+	if (res < 0)
 		goto err_hdl;
 	v4l2_info(v4l2_dev, "ADS Cadet Radio Card at 0x%x\n", dev->io);
 	return 0;