nixos/thermald: add adaptive mode

thermald >=2.3 supports the adaptive DPTF mode, in conjunction with
kernel 5.8.

nixos/modules/services/hardware/thermald.nix

@@ -23,6 +23,15 @@ in {
         default = null;
         description = "the thermald manual configuration file.";
       };
+
+      adaptive = mkOption {
+        type = types.bool;
+        default = false;
+        description = ''
+          Whether to enable adaptive mode, only working on kernel versions greater than 5.8.
+          Thermald will detect this itself, safe to enable on kernel versions below 5.8.
+        '';
+      };
     };
   };
 
@@ -39,6 +48,7 @@ in {
             --no-daemon \
             ${optionalString cfg.debug "--loglevel=debug"} \
             ${optionalString (cfg.configFile != null) "--config-file ${cfg.configFile}"} \
+            ${optionalString cfg.adaptive "--adaptive"} \
             --dbus-enable
         '';
       };