Fix internal link->iftype vs. hwaddr.arp_type handling

Wicked has two types for links. One is for its internal representation, the other is for ARP handling. Both use different numbers. But their usage was mixed and sometimes the internal enum was used for ARP and via versa. This caused errors in lldp.

Adjust all usage of ni_hwaddr_t->type and ni_linkinfo->type, use proper values as needed.