iwlwifi: split off Bz devices into their own family

These devices have some places with different behaviour
required, so split them off into their own family as they
should be.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Link: https://lore.kernel.org/r/iwlwifi.20210802215208.90257303559f.I4c4342229dcb9513099a3152605f0947423e86dc@changeid
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>