iwlwifi: FreeBSD specific sysctl export update

Update the sysctl export (also adding a mapping function) to also
print (1) for all lines the "flavor" (device_family) name and (2)
also print lines where we only have the trans cfg and not iwl cfg
as with the flavor we can match PCI IDs to firmware package and so
we can have an increased number of matches.
A side effect is that we can also have fwget(8) PCI ID matches for
firmware (flavors) not yet (publicly) existing. That will allow
us to add them at a later point while a previous release already
supports the chipsets and knows how to get the firmware for them.

Sponsored by: The FreeBSD Foundation
MFC after: 3 days