iwl3945: removed bg_post_associate work

This patch removes bg_post_associate work. A direct call
iwl3945_post_associate is made to avoid the waiting by
userspace programs.

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>