mac80211: complete scan work immediately if quiesced or suspended

It is possible that a deferred scan is queued after the queues are
flushed in __ieee80211_suspend().  The deferred scan work may be
scheduled by ROC or ieee80211_stop_poll().

To make sure don't start a new scan while suspending, check whether
we're quiescing or suspended and complete the scan immediately if
that's the case.

Signed-off-by: Luciano Coelho <luciano.coelho@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>