mac80211 : fix for iwconfig in ad-hoc mode

The patch checks interface status, if it is in IBSS_JOINED mode
show cell id it is associated with.

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