iwlwifi: do not spuriously call ieee80211_scan_completed

When a scan is aborted because the corresponding
virtual interface is removed, we may still later
attempt to tell mac80211 that the scan completed.
This is obviously wrong, since we already told it
that it was aborted, so don't do that.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>