ArduCopter: fix Failed to Init Optflow message at startup

ArduCopter/Attitude.pde

@@ -589,7 +589,7 @@ get_rate_yaw(int32_t target_rate)
 static int32_t
 get_of_roll(int32_t input_roll)
 {
-#ifdef OPTFLOW_ENABLED
+#if OPTFLOW == ENABLED
     static float tot_x_cm = 0;      // total distance from target
     static uint32_t last_of_roll_update = 0;
     int32_t new_roll = 0;
@@ -643,7 +643,7 @@ get_of_roll(int32_t input_roll)
 static int32_t
 get_of_pitch(int32_t input_pitch)
 {
-#ifdef OPTFLOW_ENABLED
+#if OPTFLOW == ENABLED
     static float tot_y_cm = 0;  // total distance from target
     static uint32_t last_of_pitch_update = 0;
     int32_t new_pitch = 0;

ArduCopter/Parameters.pde

@@ -122,7 +122,7 @@ const AP_Param::Info var_info[] PROGMEM = {
     // @Description: Setting this to Enabled(1) will enable optical flow. Setting this to Disabled(0) will disable optical flow
     // @Values: 0:Disabled,1:Enabled
     // @User: Standard
-    GSCALAR(optflow_enabled,        "FLOW_ENABLE",  OPTFLOW),
+    GSCALAR(optflow_enabled,        "FLOW_ENABLE",  DISABLED),
 
     // @Param: LOW_VOLT
     // @DisplayName: Low Voltage