thermostat: change setup seq

- default power off
- with all params set to default val on hw
- rm calibration from setup

src/thermostat/thermostat.rs

@@ -100,12 +100,10 @@ impl Thermostat{
         }
     }
     pub fn setup(&mut self) {
-        self.power_up();
+        self.power_down();
 
         self.tec_setting = Settings::default();
 
-        self.calibrate_dac_value();
-
         self.set_i(self.tec_setting.i_set);
 
         self.set_max_v(self.tec_setting.max_v_set);