AP_Frsky_Telem: send ap_status only once initialized

Same as what is found in GCS_MAVLink.cpp for copter

libraries/AP_Frsky_Telem/AP_Frsky_Telem.cpp

@@ -50,6 +50,7 @@ void AP_Frsky_Telem::init(const AP_SerialManager &serial_manager, const char *fi
         _params.fs_batt_voltage = fs_batt_voltage; // failsafe battery voltage in volts
         _params.fs_batt_mah = fs_batt_mah; // failsafe reserve capacity in mAh
         if (ap_valuep == nullptr) { // ap bit-field
+            _ap.value = 0x2000; // set "initialised" to 1 for rover and plane
             _ap.valuep = &_ap.value;
         } else {
             _ap.valuep = ap_valuep;
@@ -111,8 +112,10 @@ void AP_Frsky_Telem::send_SPort_Passthrough(void)
                 _passthrough.params_timer = AP_HAL::millis();
                 return;
             } else if ((now - _passthrough.ap_status_timer) > 500) {
+                if ((*_ap.valuep & AP_INITIALIZED_FLAG) > 0) {  // send ap status only once vehicle has been initialised
                     send_uint32(DIY_FIRST_ID+1, calc_ap_status());
                     _passthrough.ap_status_timer = AP_HAL::millis();
+                }
                 return;
             } else if ((now - _passthrough.batt_timer) > 1000) {
                 send_uint32(DIY_FIRST_ID+3, calc_batt());

libraries/AP_Frsky_Telem/AP_Frsky_Telem.h

@@ -91,6 +91,7 @@ for FrSky SPort Passthrough
 #define AP_SSIMPLE_FLAGS            0x6
 #define AP_SSIMPLE_OFFSET           4
 #define AP_ISFLYING_FLAG            0x80
+#define AP_INITIALIZED_FLAG         0x2000
 #define AP_ARMED_OFFSET             8
 #define AP_BATT_FS_OFFSET           9
 #define AP_EKF_FS_OFFSET            10