nl80211: Fix nla_nest_start conversion

Dmitry reported that the kernel could no longer parse the
scheduled scan attributes correctly after my patch to use
nla_nest_start/nla_nest_end. The reason is that the wrong
attribute is closed I accidentally made it close the full
scan config instead of just the SSID match set.

Reported-by: Dmitry Shmidt <dimitrysh@google.com>
Signed-hostap: Johannes Berg <johannes.berg@intel.com>

src/drivers/driver_nl80211.c

@@ -4004,7 +4004,7 @@ static int wpa_driver_nl80211_sched_scan(void *priv,
 				drv->filter_ssids[i].ssid_len,
 				drv->filter_ssids[i].ssid);
 
-			nla_nest_end(msg, match_sets);
+			nla_nest_end(msg, match_set_ssid);
 		}
 
 		if (params->filter_rssi) {