net80211: fix CCMP/GCMP AAD for MFP frames

Update ieee80211_crypto_init_aad() to do what 802.11-2020 says -
only mask fc[0] bits 4-6 on data frames, not on management frames.
This (with other diffs to actually negotiate MFP and configure
ath(4) for MFP + software keys) allows the CCMP path to decrypt
CCMP MFP frames in the software path.

Differential Revision: https://reviews.freebsd.org/D57799