iwlwifi: don't delay scan in IBSS mode

Scan need to be delayed only after association to allow EAPOL
exchange. We don't need the delay for IBSS mode.

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