Fix GPS RTCM instance selection

src/drivers/gps/gps.cpp

@@ -547,8 +547,13 @@ void GPS::handleInjectDataTopic()
 		for (int instance = 0; instance < _orb_inject_data_sub.size(); instance++) {
 			const bool exists = _orb_inject_data_sub[instance].advertised();
 
-			if (exists) {
-				if (_orb_inject_data_sub[instance].copy(&msg)) {
+			if (exists && _orb_inject_data_sub[instance].copy(&msg)) {
+				/* Don't select the own RTCM instance. In case it has a lower
+				 * instance number, it will be selected and will be rejected
+				 * later in the code, resulting in no RTCM injection at all.
+				 */
+				if (msg.device_id != get_device_id()) {
+					// Only use the message if it is up to date
 					if ((hrt_absolute_time() - msg.timestamp) < 5_s) {
 						// Remember that we already did a copy on this instance.
 						already_copied = true;