iwl3945: use iwl rx handlers

Patch removes duplicate rx handlers(pm_sleep and pm_debug) from 3945 and
uses handlers from iwlwifi.

Signed-off-by: Abhijeet Kolekar <abhijeet.kolekar@intel.com>
Acked-by: Samuel Ortiz <samuel.ortiz@intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>