[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.

Tested:

• Intel 7260, STA mode (2GHz)

Obtained from: dragonflybsd commit 39f8331b1a6f295291e08c377da12a8e7a5436c0