Tracker: eliminate global static GCS_MAVLINK::send_home_all

AntennaTracker/GCS_Tracker.h

@@ -14,6 +14,7 @@ public:
 
     // return GCS link at offset ofs
     GCS_MAVLINK_Tracker &chan(const uint8_t ofs) override { return _chan[ofs]; };
+    const GCS_MAVLINK_Tracker &chan(const uint8_t ofs) const override { return _chan[ofs]; };
 
     void setup_uarts(AP_SerialManager &serial_manager) override;
 

AntennaTracker/system.cpp

@@ -165,7 +165,7 @@ void Tracker::set_home(struct Location temp)
 {
     set_home_eeprom(temp);
     current_loc = temp;
-    GCS_MAVLINK::send_home_all(temp);
+    gcs().send_home(temp);
 }
 
 void Tracker::arm_servos()