ifconfig: 80211, add line break after key info

Beauty correction for verbose mode or in case we print multiple key
information to not continue with the next options directly after
as we did so far, e.g.:
AES-CCM 2:128-bit
AES-CCM 3:128-bit powersavemode ...

Sponsored-by: The FreeBSD Foundation
MFC-after: 2 weeks
Reviewed-by: adrian
Differential Revision: https://reviews.freebsd.org/D29393