mac80211: probe with correct SSID

While associated, we should probe with the SSID we're associated to,
not the scan SSID.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Acked-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>