LinuxKPI: 802.11: implement ieee80211_sn_*()

Implement ieee80211_sn_*() using the equivalent net80211 macros.
We need those implemented for at least 11n.
While here also sort all the BA functions together next to the
"sn" functions.

Sponsored by: The FreeBSD Foundation
MFC after: 3 days
Differential Revision: https://reviews.freebsd.org/D45819