net: ipx: mark expected switch fall-through

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

Signed-off-by: Gustavo A. R. Silva <garsilva@embeddedor.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipx/af_ipx.c

@@ -1867,6 +1867,7 @@ static int ipx_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg)
 		rc = -EPERM;
 		if (!capable(CAP_NET_ADMIN))
 			break;
+		/* fall through */
 	case SIOCGIFADDR:
 		rc = ipxitf_ioctl(cmd, argp);
 		break;