netX52 Single Ethernet Port Variant: Link change indication delivers uninitialized data for non-existing port

In the single PHY variant for netX52, if the link status of the exsiting port changes and consequently, a link status change indication is delivered, then the status of the non-existing port in the indication's data part contains uninitialized data.

This requires knowledge of the host of whether the targeted device has one or two Ethernet ports and thus makes a generic implementation infeasible.

For the single port variant, the link status of the non-existing port should always be set to zero.