AP_HAL_Linux: Update namespace and private

Add new interfaces for optical flow

libraries/AP_HAL_Linux/AP_HAL_Linux_Namespace.h

@@ -44,6 +44,11 @@ namespace Linux {
     class ToneAlarm;
     class Heat;
     class HeatPwm;
+    class CameraSensor;
+    class CameraSensor_Mt9v117;
+    class VideoIn;
+    class OpticalFlow_Onboard;
+    class Flow_PX4;
 }
 
 #endif // __AP_HAL_LINUX_NAMESPACE_H__

libraries/AP_HAL_Linux/AP_HAL_Linux_Private.h

@@ -36,6 +36,11 @@
 #include "Util_RPI.h"
 #include "Heat.h"
 #include "Heat_Pwm.h"
+#include "CameraSensor.h"
+#include "CameraSensor_Mt9v117.h"
+#include "VideoIn.h"
+#include "OpticalFlow_Onboard.h"
+#include "Flow_PX4.h"
 
 #endif // __AP_HAL_LINUX_PRIVATE_H__