Eahrs remove gps serial assumption

libraries/AP_ExternalAHRS/AP_ExternalAHRS.h

@@ -86,6 +86,11 @@ class AP_ExternalAHRS {
     // get serial port number, -1 for not enabled
     int8_t get_port(AvailableSensor sensor) const;
 
+    // check if a sensor type is enabled
+    bool has_sensor(AvailableSensor sensor) const {
+        return (uint16_t(sensors.get()) & uint16_t(sensor)) != 0;
+    }
+
     struct state_t {
         HAL_Semaphore sem;
 
@@ -190,11 +195,6 @@ class AP_ExternalAHRS {
 
     static AP_ExternalAHRS *_singleton;
 
-    // check if a sensor type is enabled
-    bool has_sensor(AvailableSensor sensor) const {
-        return (uint16_t(sensors.get()) & uint16_t(sensor)) != 0;
-    }
-
     // set default of EAHRS_SENSORS
     void set_default_sensors(uint16_t _sensors) {
         sensors.set_default(_sensors);

libraries/AP_GPS/AP_GPS.cpp

@@ -662,7 +662,7 @@ AP_GPS_Backend *AP_GPS::_detect_instance(uint8_t instance)
 #endif
 #if HAL_EXTERNAL_AHRS_ENABLED
     case GPS_TYPE_EXTERNAL_AHRS:
-        if (AP::externalAHRS().get_port(AP_ExternalAHRS::AvailableSensor::GPS) >= 0) {
+        if (!AP::externalAHRS().has_sensor(AP_ExternalAHRS::AvailableSensor::GPS)) {
             dstate->auto_detected_baud = false; // specified, not detected
             return NEW_NOTHROW AP_GPS_ExternalAHRS(*this, params[instance], state[instance], nullptr);
         }