can: pcan_usb_core: fix fall-through warnings for Clang

In preparation to enable -Wimplicit-fallthrough for Clang, fix a warning by
moving the "default" to the end of the "switch" statement and explicitly adding
a break statement instead of letting the code fall through to the next case.

Link: https://github.com/KSPP/linux/issues/115
Reported-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Link: http://lore.kernel.org/r/aab7cf16bf43cc7c3e9c9930d2dae850c1d07a3c.1605896059.git.gustavoars@kernel.org
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
[mkl: move default to end]
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/usb/peak_usb/pcan_usb_core.c

@@ -295,15 +295,16 @@ static void peak_usb_write_bulk_callback(struct urb *urb)
 		netif_trans_update(netdev);
 		break;
 
-	default:
-		if (net_ratelimit())
-			netdev_err(netdev, "Tx urb aborted (%d)\n",
-				   urb->status);
 	case -EPROTO:
 	case -ENOENT:
 	case -ECONNRESET:
 	case -ESHUTDOWN:
+		break;
 
+	default:
+		if (net_ratelimit())
+			netdev_err(netdev, "Tx urb aborted (%d)\n",
+				   urb->status);
 		break;
 	}