nixos/flashprog: Use mkEnableOption instead of mkOption

in

{

  options.programs.flashprog = {

    enable = lib.mkOption {

      type = lib.types.bool;

      default = false;

      description = ''

        Installs flashprog and configures udev rules for programmers

        used by flashprog.

    enable = lib.mkEnableOption ''

      configuring flashprog udev rules and

      installing flashprog as system package

    '';

    };

    package = lib.mkPackageOption pkgs "flashprog" { };

  };