mac80211: add support for tx to abort low priority scan requests

Use NL80211_SCAN_FLAG_LOW_PRIORITY flag in mac80211's scan state
machine to prematurely terminate scan operations if outbound
traffic collides. This is useful for marking background scans so
they don't affect throughput.

Signed-off-by: Sam Leffler <sleffler@chromium.org>
Signed-off-by: Amitkumar Karwar <akarwar@marvell.com>
Signed-off-by: Bing Zhao <bzhao@marvell.com>
[set feature flag only if software scan is used]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index 6327816..02e4793 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -866,6 +866,7 @@
  * @SCAN_SUSPEND: Suspend the scan and go back to operating channel to
  *	send out data
  * @SCAN_RESUME: Resume the scan and scan the next channel
+ * @SCAN_ABORT: Abort the scan and go back to operating channel
  */
 enum mac80211_scan_state {
 	SCAN_DECISION,
@@ -873,6 +874,7 @@
 	SCAN_SEND_PROBE,
 	SCAN_SUSPEND,
 	SCAN_RESUME,
+	SCAN_ABORT,
 };
 
 struct ieee80211_local {