iwlagn: Remove dependence of iwl_priv from eeprom routines.

Make the eeprom routines less dependent on the iwl_priv structure.
Don't use the priv when bus structure is sufficient.

Signed-off-by: Don Fry <donald.h.fry@intel.com>
Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>