ath6kl: fix scan operation while disconnect

If a scan operation is pending and in between a disconnect
event is received from firmware the scan results never get
sent back to cfg80211. This causes a scan failure and yields
a device/resource busy state upon retries. If a disconnect
event is received and scan is pending return the scan done
to the cfg80211 to enable futher scans to be issued.

Signed-off-by: Naveen Singh <nsingh@atheros.com>
Signed-off-by: Luis R. Rodriguez <lrodriguez@atheros.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>