mac80211 : Association with 11n hidden ssid ap.

This patch fixes the association problem with 11n hidden ssid ap.
Patch fixes the problem of associating with hidden ssid when
all three parameters ap,essid and channel are given to iwconfig.
This patch removes the condition of checking three parameters
and always checks for bss in bss list while associating.

Signed-off-by: Abhijeet Kolekar <abhijeet.kolekar@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>