iwlwifi: changing EEPROM layout handling

This patch
1. changes the current EEPROM handling through a single HW struct
layout representation, to more general approach, treating the EEPROM
image as a flat bytes array, handling this image through ops functions
and offsets.
2. Eeprom is dynamically allocated accroding HW type

Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Ron Rindjunsky <ron.rindjunsky@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>