add rl_config.device param to support use apple chip GPU

freqtrade/freqai/prediction_models/ReinforcementLearner.py

@@ -58,10 +58,16 @@ class ReinforcementLearner(BaseReinforcementLearningModel):
                              net_arch=self.net_arch)
 
         if dk.pair not in self.dd.model_dictionary or not self.continual_learning:
+            kwargs = self.freqai_info.get('model_training_parameters', {})
+
+            # set device if device is not None
+            if self.device != '':
+                kwargs['device'] = self.device
+
             model = self.MODELCLASS(self.policy_type, self.train_env, policy_kwargs=policy_kwargs,
                                     tensorboard_log=Path(
                                         dk.full_path / "tensorboard" / dk.pair.split('/')[0]),
-                                    **self.freqai_info.get('model_training_parameters', {})
+                                    **kwargs
                                     )
         else:
             logger.info('Continual training activated - starting training from previously '