mac80211: ignore cqm during csa

It is not guaranteed that multi-vif channel
switching is tightly synchronized. It makes sense
to ignore cqm (missing beacons, et al) while csa
is progressing and re-check it after it completes.

Signed-off-by: Michal Kazior <michal.kazior@tieto.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>