nl80211: fix station_info pertid memory leak

When dumping stations, memory allocated for station_info's
pertid member will leak if the nl80211 header cannot be added to
the sk_buff due to insufficient tail room.

I noticed this leak in the kmalloc-2048 cache.

Cc: stable@vger.kernel.org
Fixes: 8689c05 ("cfg80211: dynamically allocate per-tid stats for station info")
Signed-off-by: Andy Strohman <andy@uplevelsystems.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/wireless/nl80211.c

@@ -4859,8 +4859,10 @@ static int nl80211_send_station(struct sk_buff *msg, u32 cmd, u32 portid,
 	struct nlattr *sinfoattr, *bss_param;
 
 	hdr = nl80211hdr_put(msg, portid, seq, flags, cmd);
-	if (!hdr)
+	if (!hdr) {
+		cfg80211_sinfo_release_content(sinfo);
 		return -1;
+	}
 
 	if (nla_put_u32(msg, NL80211_ATTR_IFINDEX, dev->ifindex) ||
 	    nla_put(msg, NL80211_ATTR_MAC, ETH_ALEN, mac_addr) ||