if_iwm - Sync nvm parsing code with Linux iwlwifi.

if_iwm - Sync nvm parsing code with Linux iwlwifi.

* sc->sc_nvm becomes sc->nvm_data and is now a pointer instead of an
  inlined struct.

* Add sc->eeprom_size and sc->nvm_hw_section_num configuration values to
  struct iwm_softc.

* For now continue to avoid negative error return-values, and use pointer
  variables for some return values, as before.

* Continue to omit LAR (location aware regulatory) related code as well.