sd: fix an error return in probe()

If device_add() fails then it should return the error code but instead
the current code returns success.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Tomas Henzl <thenzl@redhat.com>
Signed-off-by: James Bottomley <JBottomley@Odin.com>

drivers/scsi/sd.c

@@ -2988,7 +2988,8 @@ static int sd_probe(struct device *dev)
 	sdkp->dev.class = &sd_disk_class;
 	dev_set_name(&sdkp->dev, "%s", dev_name(dev));
 
-	if (device_add(&sdkp->dev))
+	error = device_add(&sdkp->dev);
+	if (error)
 		goto out_free_index;
 
 	get_device(dev);