mac80211: Do not restart scheduled scan if multiple scan plans are set

If multiple scan plans were set for scheduled scan, do not restart
scheduled scan on reconfig because it is possible that some scan
plans were already completed and there is no need to run them all
over again. Instead, notify userspace that scheduled scan stopped
so it can configure new scan plans for scheduled scan.

Signed-off-by: Avraham Stern <avraham.stern@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>