Copter: update for new OptFlow API

ArduCopter/ArduCopter.pde

@@ -314,8 +314,8 @@ AP_Mission mission(ahrs, &start_command, &verify_command, &exit_mission);
 ////////////////////////////////////////////////////////////////////////////////
 // Optical flow sensor
 ////////////////////////////////////////////////////////////////////////////////
-#if OPTFLOW == ENABLED && CONFIG_HAL_BOARD == HAL_BOARD_PX4
+#if OPTFLOW == ENABLED
-static AP_OpticalFlow_PX4 optflow(ahrs);
+static OpticalFlow optflow;
 #endif
 
 // gnd speed limit required to observe optical flow sensor limits

ArduCopter/config.h

@@ -388,7 +388,7 @@
 //////////////////////////////////////////////////////////////////////////////
 //  OPTICAL_FLOW
 #ifndef OPTFLOW
- #if CONFIG_HAL_BOARD == HAL_BOARD_PX4
+ #if HAL_CPU_CLASS >= HAL_CPU_CLASS_75
   # define OPTFLOW       ENABLED
  #else
   # define OPTFLOW       DISABLED