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
Reviewed by: adrian
Differential Revision: https://reviews.freebsd.org/D50553

(cherry picked from commit 54ad06cad10c3822784389b0956f92a1c7041abd)