ArduSub: remove pointless init_optflow wrapper

Hiding a one-line call in a wrapper just adds size to the build

ArduSub/Sub.h

@@ -550,9 +550,6 @@ private:
     void init_rangefinder(void);
     void read_rangefinder(void);
     bool rangefinder_alt_ok(void) const;
-#if OPTFLOW == ENABLED
-    void init_optflow();
-#endif
     void terrain_update();
     void terrain_logging();
     void init_ardupilot() override;

ArduSub/sensors.cpp

@@ -86,15 +86,6 @@ void Sub::rpm_update(void)
 }
 #endif
 
-// initialise optical flow sensor
-#if OPTFLOW == ENABLED
-void Sub::init_optflow()
-{
-    // initialise optical flow sensor
-    optflow.init(MASK_LOG_OPTFLOW);
-}
-#endif      // OPTFLOW == ENABLED
-
 void Sub::accel_cal_update()
 {
     if (hal.util->get_soft_armed()) {

ArduSub/system.cpp

@@ -94,9 +94,9 @@ void Sub::init_ardupilot()
     wp_nav.set_terrain(&terrain);
 #endif
 
-    // init the optical flow sensor
 #if OPTFLOW == ENABLED
-    init_optflow();
+    // initialise optical flow sensor
+    optflow.init(MASK_LOG_OPTFLOW);
 #endif
 
 #if HAL_MOUNT_ENABLED