initrd: Include filesystem support for /nix, /var etc.

nixos/modules/tasks/filesystems.nix

@@ -124,13 +124,6 @@ in
       description = "Names of supported filesystem types.";
     };
 
-    boot.initrd.supportedFilesystems = mkOption {
-      default = [ ];
-      example = [ "btrfs" ];
-      type = types.listOf types.string;
-      description = "Names of supported filesystem types in the initial ramdisk.";
-    };
-
   };
 
 
@@ -140,10 +133,6 @@ in
 
     boot.supportedFilesystems = map (fs: fs.fsType) fileSystems;
 
-    boot.initrd.supportedFilesystems =
-      map (fs: fs.fsType)
-        (filter (fs: fs.mountPoint == "/" || fs.neededForBoot) fileSystems);
-
     # Add the mount helpers to the system path so that `mount' can find them.
     system.fsPackages = [ pkgs.dosfstools ];