iwlwifi: fix IBSS association flow

This patch fixes regression caused by
'iwlwifi: send ADD_STA before RXON with assoc bit' patch.
RXON associated wasn't IBSS flow.

Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Assaf Krauss <assaf.krauss@intel.com>
Signed-off-by: Zhu Yi <yi.zhu@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>