80211: consistently spell 80P80

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