cosa: missing error code on failure in probe()

If register_hdlc_device() fails, the current code returns 0 but we
should return an error code instead.
Signed-off-by: NDan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/wan/cosa.c

@@ -589,7 +589,8 @@ static int cosa_probe(int base, int irq, int dma)
 		chan->netdev->base_addr = chan->cosa->datareg;
 		chan->netdev->irq = chan->cosa->irq;
 		chan->netdev->dma = chan->cosa->dma;
-		if (register_hdlc_device(chan->netdev)) {
+		err = register_hdlc_device(chan->netdev);
+		if (err) {
 			netdev_warn(chan->netdev,
 				    "register_hdlc_device() failed\n");
 			free_netdev(chan->netdev);