AP_MSP: move arming status to MSP telemetry base class

libraries/AP_MSP/AP_MSP_Telem_Backend.cpp

@@ -577,6 +577,16 @@ void AP_MSP_Telem_Backend::msp_handle_airspeed(const MSP::msp_airspeed_data_mess
 #endif
 }
 
+uint32_t AP_MSP_Telem_Backend::get_osd_flight_mode_bitmask(void)
+{
+    // Note: we only set the BOXARM bit (bit 0) which is the same for BF, INAV and DJI VTX
+    // When armed we simply return 1 (1 == 1 << 0)
+    if (hal.util->get_soft_armed()) {
+        return 1U;
+    }
+    return 0U;
+}
+
 MSPCommandResult AP_MSP_Telem_Backend::msp_process_out_api_version(sbuf_t *dst)
 {
     const struct {

libraries/AP_MSP/AP_MSP_Telem_Backend.h

@@ -184,11 +184,9 @@ protected:
     void msp_handle_airspeed(const MSP::msp_airspeed_data_message_t &pkt);
 
     // implementation specific helpers
+    // we only set arming status
     // custom masks are needed for vendor specific settings
-    virtual uint32_t get_osd_flight_mode_bitmask(void)
+    virtual uint32_t get_osd_flight_mode_bitmask(void);
-    {
-        return 0;
-    }
 
     virtual bool is_scheduler_enabled() const = 0;                            // only osd backends should allow a push type telemetry
     virtual bool use_msp_thread() const {return true;};                       // is this backend hanlded by the MSP thread?

libraries/AP_MSP/AP_MSP_Telem_DJI.cpp

@@ -69,14 +69,9 @@ void AP_MSP_Telem_DJI::hide_osd_items(void)
 
 uint32_t AP_MSP_Telem_DJI::get_osd_flight_mode_bitmask(void)
 {
-    uint32_t mode_mask = 0;
+    uint32_t mode_mask = AP_MSP_Telem_Backend::get_osd_flight_mode_bitmask();
     const AP_Notify& notify = AP::notify();
 
-    // set arming status
-    if (notify.flags.armed) {
-        BIT_SET(mode_mask, DJI_FLAG_ARM);
-    }
-
     // check failsafe
     if (notify.flags.failsafe_battery || notify.flags.failsafe_gcs || notify.flags.failsafe_radio || notify.flags.ekf_bad ) {
         BIT_SET(mode_mask, DJI_FLAG_FS);