nixos/hardware/rtl-sdr: Fix description

nixos/modules/hardware/rtl-sdr.nix

@@ -5,10 +5,14 @@ let
 
 in {
   options.hardware.rtl-sdr = {
-    enable = lib.mkEnableOption ''
-      Enables rtl-sdr udev rules, ensures 'plugdev' group exists, and blacklists DVB kernel modules.
-      This is a prerequisite to using devices supported by rtl-sdr without being root, since rtl-sdr USB descriptors will be owned by plugdev through udev.
-    '';
+    enable = lib.mkOption {
+      type = lib.types.bool;
+      default = false;
+      description = ''
+        Enables rtl-sdr udev rules, ensures 'plugdev' group exists, and blacklists DVB kernel modules.
+        This is a prerequisite to using devices supported by rtl-sdr without being root, since rtl-sdr USB descriptors will be owned by plugdev through udev.
+       '';
+    };
   };
 
   config = lib.mkIf cfg.enable {