mac80211: fix missing sta_lock in __sta_info_destroy

mac80211: fix missing sta_lock in __sta_info_destroy

commit 4bae7d976976fa52d345805ba686934cd548343e upstream.

Since my commit 34e895075e21be3e21e71d6317440d1ee7969ad0
("mac80211: allow station add/remove to sleep") there is
a race in mac80211 when it clears the TIM bit because a
sleeping station disconnected, the spinlock isn't held
around the relevant code any more. Use the right API to
acquire the spinlock correctly.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>