cfg80211: consider existing DFS interfaces

It was possible to break interface combinations in
the following way:

 combo 1: iftype = AP, num_ifaces = 2, num_chans = 2,
 combo 2: iftype = AP, num_ifaces = 1, num_chans = 1, radar = HT20

With the above interface combinations it was
possible to:

 step 1. start AP on DFS channel by matching combo 2
 step 2. start AP on non-DFS channel by matching combo 1

This was possible beacuse (step 2) did not consider
if other interfaces require radar detection.

The patch changes how cfg80211 tracks channels -
instead of channel itself now a complete chandef
is stored.

Signed-off-by: Michal Kazior <michal.kazior@tieto.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
diff --git a/net/wireless/core.h b/net/wireless/core.h
index 8a820f9..9895ab1 100644
--- a/net/wireless/core.h
+++ b/net/wireless/core.h
@@ -443,7 +443,8 @@
 void
 cfg80211_get_chan_state(struct wireless_dev *wdev,
 		        struct ieee80211_channel **chan,
-		        enum cfg80211_chan_mode *chanmode);
+		        enum cfg80211_chan_mode *chanmode,
+		        u8 *radar_detect);
 
 int cfg80211_set_monitor_channel(struct cfg80211_registered_device *rdev,
 				 struct cfg80211_chan_def *chandef);