net: appletalk: cops: mark expected switch fall-through

In preparation to enabling -Wimplicit-fallthrough, mark switch
cases where we are expecting to fall through.

Notice that, in this particular case, the fall-through annotation
is placed at the beginning of the code comment, which is what
GCC is expecting to find.

Warning level 3 was used: -Wimplicit-fallthrough=3

This patch is part of the ongoing efforts to enabling
-Wimplicit-fallthrough.
Signed-off-by: NGustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/appletalk/cops.c

@@ -301,7 +301,7 @@ static int __init cops_probe1(struct net_device *dev, int ioaddr)
 			dev->irq = cops_irq(ioaddr, board);
 			if (dev->irq)
 				break;
-			/* No IRQ found on this port, fallthrough */
+			/* fall through - Once no IRQ found on this port. */
 		case 1:
 			retval = -EINVAL;
 			goto err_out;