iwlwifi: mvm: support ucode load for family_8000 B0 only

The ucode load flow changed for B0 hardware step.
Change the code accordingly.

Signed-off-by: Eran Harary <eran.harary@intel.com>
Signed-off-by: Liad Kaufman <liad.kaufman@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>