mac80211: fix memory leak

mac80211: fix memory leak

commit ea32f065bd3e3e09f0bcb3042f1664caf6b3e233 upstream.

On error we jumped to the error label and returned the error code but we
missed releasing sinfo.

Fixes: 5fe74014172d ("mac80211: avoid excessive stack usage in sta_info")
Reviewed-by: Julian Calaby <julian.calaby@gmail.com>
Signed-off-by: Sudip Mukherjee <sudip@vectorindia.org>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
[bwh: Backported to 3.2: there's no out_err label but there is another
 error case that would leak sinfo]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>