Purge more stray embedded $FreeBSD$ strings

These do not use __FBSDID but instead use bare char arrays.

Reviewed by: imp, emaste
Differential Revision: https://reviews.freebsd.org/D41957

80211: non-functional changes

Sort a few VHT160 and 80+80 lines, update some comments, and remove
a superfluous ','.

No functional changes intended.

MFC after: 1 week
Sponsored by: The FreeBSD Foundation

80211: consistently spell 80P80

The standard uses 80+80 and 80p80 but nowhere 80_80.
Switch the latter to 80P80 for all the macros and comments refering
to #defined flags which I could find.
The only place we leave as 80p80 is the ifconfig command line arguments
as we spell them all in lower case.
Ideally we would use 80+80 for any interactions with the user and
80P80 for anything internal but let us not confuse parsers and
hence avoid the '+' in either case.

Reviewed by: adrian, gnn
MFC after: 2 weeks
Sponsored by: Rubicon Communications, LLC (d/b/a "Netgate")
Differential Revision: https://reviews.freebsd.org/D26001

[lib80211] fix a missing cleanup path.

PR: lib/218655
Reported by: <valentin.vergez@stormshield.eu>

[lib80211] add VHT bands and channel flags.

This is preparation work for 11ac support. The regulatory database
needs to know about VHT channel flags and 80MHz (and later 160MHz)
available channel bands.

Whilst here, add the 2GHz VHT band (which is a terrible, terrible vendor
extension that almost all vendors do) just in preparation, even though
I don't (yet) plan on supporting it.

Add lib80211, a small (but hopefully soon to grow) set of library
routines to interface with net80211.

This is all from the ifconfig program; the duplicate code from ifconfig
will be removed when it starts using this API.

Differential Revision: https://reviews.freebsd.org/D4290