nl80211: Update freq only when CSA completes

nl80211: Update freq only when CSA completes

In the case of the ap_csa_disable test, I frequently see
failures due to the kernel *not* having switched, but the
CSA-STARTED event having been processed, and thus the
frequency having been updated already.

This is wrong at least for AP mode, the frequency we store
for this case internally in nl80211 should only be updated
when the channel switch completes, otherwise we end up in
a situation where the switch is aborted and the kernel is
thus on the old channel, but the internal information has
been updated and every subsequent mgmt-frame TX fails due
to being tagged with the wrong channel.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>