ld_drive: add setup fn

src/laser_diode/ld_drive.rs

@@ -71,6 +71,12 @@ impl LD_Drive{
         }
     }
 
+    pub fn setup(&mut self) {
+        self.power_down();
+        self.ld_set_i(ElectricCurrent::new::<milliampere>(0.0));
+        self.ld_short();
+    }
+
     pub fn power_up(&mut self){
         self.ctrl.power_up();
     }