ifconfig: 802.11: also print IEEE80211_CIPHER_AES_GCM_128 information

While we currently do not print the STA unicast key (PTK) we will not
see this but it is for fullness and in preparations for follow-up
hanges.

Sponsored by: The FreeBSD Foundation
MFC after: 3 days
Reviewed by: adrian
Differential Revision: https://reviews.freebsd.org/D50553