iwl3945: Use iwl-eeprom.c routines

By adding the eeprom ops to the 3945 code, we can now use the iwlcore eeprom
routines (defined in iwl-eeprom.c).
We also removed the heavy eeprom39 reference from iwl_priv and use the eeprom
pointer instead.

Signed-off-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>