AP_Notify: define external led pins for non APM boards

resolves compiler errors

libraries/AP_Notify/ExternalLED.h

@@ -23,15 +23,20 @@
 #include <AP_Param.h>
 
 #if CONFIG_HAL_BOARD == HAL_BOARD_APM2
- #define EXTERNAL_LED_ARMED   61      // Armed LED - AN7
- #define EXTERNAL_LED_GPS     60      // GPS LED - AN6
- #define EXTERNAL_LED_MOTOR1  58      // Motor1 LED - AN4
- #define EXTERNAL_LED_MOTOR2  62      // Motor2 LED - AN8
+ #define EXTERNAL_LED_ARMED   61    // Armed LED - AN7
+ #define EXTERNAL_LED_GPS     60    // GPS LED - AN6
+ #define EXTERNAL_LED_MOTOR1  58    // Motor1 LED - AN4
+ #define EXTERNAL_LED_MOTOR2  62    // Motor2 LED - AN8
 #elif CONFIG_HAL_BOARD == HAL_BOARD_APM1
- #define EXTERNAL_LED_GPS     64  // GPS LED - AN10
- #define EXTERNAL_LED_ARMED   65  // Armed LED - AN11
- #define EXTERNAL_LED_MOTOR1  62  // Motor1 LED - AN8
- #define EXTERNAL_LED_MOTOR2  66  // Motor2 LED - AN12
+ #define EXTERNAL_LED_GPS     64    // GPS LED - AN10
+ #define EXTERNAL_LED_ARMED   65    // Armed LED - AN11
+ #define EXTERNAL_LED_MOTOR1  62    // Motor1 LED - AN8
+ #define EXTERNAL_LED_MOTOR2  66    // Motor2 LED - AN12
+#else
+ #define EXTERNAL_LED_GPS     0     // pin definitions to allow this lib to build for
+ #define EXTERNAL_LED_ARMED   0     // for other boards besides APM1, APM2 even though
+ #define EXTERNAL_LED_MOTOR1  0     // they will never be used
+ #define EXTERNAL_LED_MOTOR2  0
 #endif
 
 class ExternalLED