iwl3945: check ucode load error code

Check successful completion of BSM loading. Give a chance to
load BSM again. If BSM loading is unsuccessful we should exit
and not initilize NIC. Before this checking even if the BSM loading failed
driver tries to initilize the NIC which should not be the case.

Signed-off-by: Abhijeet Kolekar <abhijeet.kolekar@intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>