nixos/undervolt: add turbo option

nixos/modules/services/hardware/undervolt.nix

@@ -12,6 +12,7 @@ let
     inherit (cfg)
       verbose
       temp
+      turbo
       ;
     # `core` and `cache` are both intentionally set to `cfg.coreOffset` as according to the undervolt docs:
     #
@@ -105,6 +106,14 @@ in
       '';
     };
 
+    turbo = mkOption {
+      type = types.nullOr types.int;
+      default = null;
+      description = lib.mdDoc ''
+        Changes the Intel Turbo feature status (1 is disabled and 0 is enabled).
+      '';
+    };
+
     p1.limit = mkOption {
       type = with types; nullOr int;
       default = null;