bss->freq was not updated for IBSS, so whatever old value was stored
from a previous AP mode operation could end up having been used as the
channel when trying to send Authentication frames in an RSN IBSS. This
resulted in the frame not sent (cfg80211 rejects it) and potentially not
being able to re-establish connection due to 4-way handshake failing
with replay counter mismatches. Fix this by learning the operating
channel of the IBSS both when join event is received and when a
management frame is being transmitted since the IBSS may have changed
channels due to merges.
Signed-off-by: Jouni Malinen <j@w1.fi>