iwlwifi: 8000: add default NVM file name in family 8000

The 8000 family products need a file on the file system
which is used as NVM. This file is a must, if no filename
is supplied as module parameter, use a default filename.

Signed-off-by: Eran Harary <eran.harary@intel.com>
Reviewed-by: Dor Shaish <dor.shaish@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>