mac80211: only cancel software-based scans on suspend

Otherwise the hardware scan handler could access an invalid scan request
structure.  The driver should cancel any pending hardware scans during
the suspend process anyway, so also add a warning if the hardware scan
is still pending when the device resumes.

Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/net/mac80211/pm.c b/net/mac80211/pm.c
index d287fde..ce671df 100644
--- a/net/mac80211/pm.c
+++ b/net/mac80211/pm.c
@@ -12,7 +12,8 @@
 	struct ieee80211_sub_if_data *sdata;
 	struct sta_info *sta;
 
-	ieee80211_scan_cancel(local);
+	if (unlikely(test_bit(SCAN_SW_SCANNING, &local->scanning)))
+		ieee80211_scan_cancel(local);
 
 	ieee80211_stop_queues_by_reason(hw,
 			IEEE80211_QUEUE_STOP_REASON_SUSPEND);