Add digital gpio related fns to Current source

- power_up
- power_down
- ld_short_enable
- ld_short_disable
    - Rev0_2 has hardware connection bug for LD_EN net.
    - laser driver power will always be enabled

src/laser_diode/current_sources.rs

@@ -60,4 +60,26 @@ impl CurrentSource {
             pins_adc: pins_adc,
         }
     }
+
+    pub fn power_up(&mut self) {
+        self.phy.current_source_ldo_en_pin.set_high();
+    }
+
+    #[deprecated(note=
+        "To be removed when rev0_3 has arrived
+        Rev0_2 has hardware connection bug for LD_EN.
+        LD_EN will always be enabled.")]
+    pub fn power_down(&mut self) {
+        self.phy.current_source_ldo_en_pin.set_low();
+    }
+
+    // LD Terminals are shorted together
+    pub fn ld_short_enable(&mut self) {
+        self.phy.current_source_short_pin.set_low();
+    }
+
+    // LD Current flows from anode to cathode
+    pub fn ld_short_disable(&mut self) {
+        self.phy.current_source_short_pin.set_high();
+    }
 }