AP_SerialLED: add defines for some AP_Notify LED libraries

allow ProfiLEDs (serial and SPI) and NeoPixel to be compiled out

libraries/AP_SerialLED/AP_SerialLED.cpp

@@ -17,6 +17,9 @@
  */
 
 #include "AP_SerialLED.h"
+
+#if AP_SERIALLED_ENABLED
+
 #include <AP_Math/AP_Math.h>
 #include "SRV_Channel/SRV_Channel.h"
 
@@ -65,3 +68,5 @@ void AP_SerialLED::send(uint8_t chan)
     }
 
 }
+
+#endif  // AP_SERIALLED_ENABLED

libraries/AP_SerialLED/AP_SerialLED.h

@@ -17,6 +17,12 @@
  */
 #pragma once
 
+#include <AP_HAL/AP_HAL_Boards.h>
+
+#include "AP_SerialLED_config.h"
+
+#if AP_SERIALLED_ENABLED
+
 #include <stdint.h>
 
 // limit number of LEDs, mostly to keep DMA memory consumption within
@@ -46,3 +52,5 @@ public:
 private:
     static AP_SerialLED singleton;
 };
+
+#endif  // AP_SERIALLED_ENABLED

libraries/AP_SerialLED/AP_SerialLED_config.h

@@ -0,0 +1,7 @@
+#pragma once
+
+#include <AP_HAL/AP_HAL_Boards.h>
+
+#ifndef AP_SERIALLED_ENABLED
+#define AP_SERIALLED_ENABLED 1
+#endif