mac80211: add post_channel_switch driver operation

As a counterpart to the pre_channel_switch operation, add a
post_channel_switch operation.  This allows the drivers to go back to
a normal configuration after the channel switch is completed.

Signed-off-by: Luciano Coelho <luciano.coelho@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
diff --git a/net/mac80211/mlme.c b/net/mac80211/mlme.c
index d23d6d9..cb1a8c3 100644
--- a/net/mac80211/mlme.c
+++ b/net/mac80211/mlme.c
@@ -1010,6 +1010,15 @@
 		sdata->csa_block_tx = false;
 	}
 
+	ret = drv_post_channel_switch(sdata);
+	if (ret) {
+		sdata_info(sdata,
+			   "driver post channel switch failed, disconnecting\n");
+		ieee80211_queue_work(&local->hw,
+				     &ifmgd->csa_connection_drop_work);
+		goto out;
+	}
+
 	ieee80211_sta_reset_beacon_monitor(sdata);
 	ieee80211_sta_reset_conn_monitor(sdata);