iwlwifi: remove macros containing offsets from eeprom struct

A user needing to access these fields can use offsetof() for
access. The comments still contain the offset to assist with
debugging.

Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
CC: Michael Buesch <mb@bu3sch.de>
Signed-off-by: Assaf Krauss <assaf.krauss@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>