iwlwifi: Change define and struct names in iwl-eeprom-parse.h

Since we will have several forms of NVM (EEPROM, OTP, etc.)
and they will have different layouts, make the parsed data
more generic. This allows functional code to be independent
of a specific layout.

Also change some variables and function names from having
"eeprom" to "nvm" in their name.

Signed-off-by: Eytan Lifshitz <eytan.lifshitz@intel.com>
Reviewed-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>