GCS_MAVLink: bind receivers directly via AP_RCProtocol library

... rather than via RC_Channels and the HAL and *then* to the AP_RCProtocol library...

libraries/GCS_MAVLink/GCS_Common.cpp

@@ -3559,7 +3559,7 @@ MAV_RESULT GCS_MAVLINK::handle_flight_termination(const mavlink_command_int_t &p
 #endif
 }
 
-#if AP_RC_CHANNEL_ENABLED
+#if AP_RCPROTOCOL_ENABLED
 /*
   handle a R/C bind request (for spektrum)
  */
@@ -3568,12 +3568,12 @@ MAV_RESULT GCS_MAVLINK::handle_START_RX_PAIR(const mavlink_command_int_t &packet
     // initiate bind procedure. We accept the DSM type from either
     // param1 or param2 due to a past mixup with what parameter is the
     // right one
-    if (!RC_Channels::receiver_bind(packet.param2>0?packet.param2:packet.param1)) {
-        return MAV_RESULT_FAILED;
-    }
+    const int dsmMode = (packet.param2 > 0) ? packet.param2 : packet.param1;
+    AP::RC().start_bind(dsmMode);
+
     return MAV_RESULT_ACCEPTED;
 }
-#endif  // AP_RC_CHANNEL_ENABLED
+#endif  // AP_RCPROTOCOL_ENABLED
 
 uint64_t GCS_MAVLINK::timesync_receive_timestamp_ns() const
 {
@@ -5578,7 +5578,7 @@ MAV_RESULT GCS_MAVLINK::handle_command_int_packet(const mavlink_command_int_t &p
         return handle_command_set_ekf_source_set(packet);
 #endif
 
-#if AP_RC_CHANNEL_ENABLED
+#if AP_RCPROTOCOL_ENABLED
     case MAV_CMD_START_RX_PAIR:
         return handle_START_RX_PAIR(packet);
 #endif