LinuxKPI: 802.11: correct HT protection fields

It seems during the initial buildup of the file, the defines were
either mixed or not flagged as "FIXME".
Define the values through to the net80211 definitions and also
annotate them by at least some standards reference.

Fixes: 6b4cac814e32f
Reviewed by: cc
Differential Revision: https://reviews.freebsd.org/D43658

(cherry picked from commit 53eb2c63c9628f7f19d88d759e1932c10c9f08af)