ifconfig: ifieee80211: print bssid name

In certain setups (e.g., autonomous APs) it is extremly helpful to have
a way to map the BSSIDs to names for both normal status output as well
as the scan list. This often allows a quicker overview than remembering
(or manually looking up) BSSIDs.
Call ether_ntohost() on the bssid and consult /etc/ethers
and print "(name)" after the bssid for the status output and "(name)"
at the end of the line after the IE list.

MFC after: 10 days
Reviewed by: adrian, cy
Differential Revision: https://reviews.freebsd.org/D39192