net: 3c509: Fix fall-through warnings for Clang

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

---
Changes in RESEND:
- None. Resendig now that net-next is open.

 drivers/net/ethernet/3com/3c509.c | 1 +
 1 file changed, 1 insertion(+)

index 53e1f7e07959..96cc5fc36eb5 100644
@@ -1051,6 +1051,7 @@ el3_netdev_get_ecmd(struct net_device *dev, struct ethtool_link_ksettings *cmd)
 		break;
 	case 3:
 		cmd->base.port = PORT_BNC;
+		break;
 	default:
 		break;
 	}

2.27.0