nixos/firmware: mention enableAllFirmware including unfree packages

  options = {

    hardware.enableAllFirmware = lib.mkEnableOption "all firmware regardless of license";

    hardware.enableAllFirmware = lib.mkOption {

      default = false;

      example = true;

      description = ''

        Whether to enable all firmware, including [unfree packages that must be explictly allowed](https://nixos.org/manual/nixpkgs/unstable/#sec-allow-unfree).

        Alternatively, use the {option}`hardware.enableRedistributableFirmware` option.

      '';

      type = lib.types.bool;

    };

    hardware.enableRedistributableFirmware =

      lib.mkEnableOption "firmware with a license allowing redistribution"