cfg80211: simplify and correct P2P-Device scan check

If the driver for some reason successfully finishes
scanning while in p2p_stop_device(), cfg80211 will
still set it to aborted. Simplify this code using the
new 'notified' value and only mark it aborted in case
the driver didn't notify cfg80211 at all (in which
case we also leak the request to not crash, this is
a driver bug.)

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