HAL_Empty: fixed I2C get_device() interface

libraries/AP_HAL_Empty/I2CDevice.h

@@ -83,7 +83,10 @@ public:
     I2CDeviceManager() { }
 
     /* AP_HAL::I2CDeviceManager implementation */
-    AP_HAL::OwnPtr<AP_HAL::I2CDevice> get_device(uint8_t bus, uint8_t address)
+    AP_HAL::OwnPtr<AP_HAL::I2CDevice> get_device(uint8_t bus, uint8_t address,
+                                                 uint32_t bus_clock=400000,
+                                                 bool use_smbus = false,
+                                                 uint32_t timeout_ms=4) override
     {
         return nullptr;
     }