AP_InertialSensor: fixed default health functions

this fixes INS on APM1. Thanks to Mike McCauley for noticing this!

libraries/AP_InertialSensor/AP_InertialSensor.cpp

@@ -655,24 +655,5 @@ void AP_InertialSensor::_calculate_trim(Vector3f accel_sample, float& trim_roll,
     }
 }
 
-/**
-   default versions of multi-device accessor functions
- */
-bool AP_InertialSensor::get_gyro_health(uint8_t instance) const
-{
-    if (instance != 0) {
-        return false;
-    }
-    return healthy();
-}
-
-bool AP_InertialSensor::get_accel_health(uint8_t instance) const
-{
-    if (instance != 0) {
-        return false;
-    }
-    return healthy();
-}
-
 #endif // __AVR_ATmega1280__
 

libraries/AP_InertialSensor/AP_InertialSensor.h

@@ -110,11 +110,11 @@ public:
     virtual void       set_accel(const Vector3f &accel) {}
 
     // multi-device interface
-    virtual bool get_gyro_health(uint8_t instance) const;
+    virtual bool get_gyro_health(uint8_t instance) const { return true; }
     bool get_gyro_health(void) const { return get_gyro_health(_get_primary_gyro()); }
     virtual uint8_t get_gyro_count(void) const { return 1; };
 
-    virtual bool get_accel_health(uint8_t instance) const;
+    virtual bool get_accel_health(uint8_t instance) const { return true; }
     bool get_accel_health(void) const { return get_accel_health(_get_primary_accel()); }
     virtual uint8_t get_accel_count(void) const { return 1; };
 

libraries/AP_InertialSensor/AP_InertialSensor_MPU6000.h

@@ -32,6 +32,8 @@ public:
 
     uint16_t error_count(void) const { return _error_count; }
     bool healthy(void) const { return _error_count <= 4; }
+    bool get_gyro_health(uint8_t instance) const { return healthy(); }
+    bool get_accel_health(uint8_t instance) const { return healthy(); }
 
 protected:
     uint16_t                    _init_sensor( Sample_rate sample_rate );