mac80211: move csa counters from sdata to beacon/presp

Having csa counters part of beacon and probe_resp
structures makes it easier to get rid of possible
races between setting a beacon and updating
counters on SMP systems by guaranteeing counters
are always consistent against given beacon struct.

While at it relax WARN_ON into WARN_ON_ONCE to
prevent spamming logs and racing.

Signed-off-by: Michal Kazior <michal.kazior@tieto.com>
[remove pointless array check]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
diff --git a/net/mac80211/ibss.c b/net/mac80211/ibss.c
index 18ee0a2..713485f 100644
--- a/net/mac80211/ibss.c
+++ b/net/mac80211/ibss.c
@@ -143,7 +143,7 @@
 		*pos++ = csa_settings->block_tx ? 1 : 0;
 		*pos++ = ieee80211_frequency_to_channel(
 				csa_settings->chandef.chan->center_freq);
-		sdata->csa_counter_offset_beacon[0] = (pos - presp->head);
+		presp->csa_counter_offsets[0] = (pos - presp->head);
 		*pos++ = csa_settings->count;
 	}