drivers/leds: Make initialization conditional on presence, not pin

The LEDx_PIN may still be defined (eg. on the particle-mesh family
because it is used to configure the PWM pins); the IS_PRESENT macro
performs the stricter check ov testing for an _ON function.

drivers/periph_common/init_leds.c

@@ -17,7 +17,7 @@
  * @}
  */
 
-#include "board.h"
+#include "led.h"
 #include "periph/gpio.h"
 #include "kernel_defines.h"
 
@@ -35,28 +35,28 @@ void led_init(void)
         return;
     }
 
-#ifdef LED0_PIN
+#ifdef LED0_IS_PRESENT
     LED_INIT(0);
 #endif
-#ifdef LED1_PIN
+#ifdef LED1_IS_PRESENT
     LED_INIT(1);
 #endif
-#ifdef LED2_PIN
+#ifdef LED2_IS_PRESENT
     LED_INIT(2);
 #endif
-#ifdef LED3_PIN
+#ifdef LED3_IS_PRESENT
     LED_INIT(3);
 #endif
-#ifdef LED4_PIN
+#ifdef LED4_IS_PRESENT
     LED_INIT(4);
 #endif
-#ifdef LED5_PIN
+#ifdef LED5_IS_PRESENT
     LED_INIT(5);
 #endif
-#ifdef LED6_PIN
+#ifdef LED6_IS_PRESENT
     LED_INIT(6);
 #endif
-#ifdef LED7_PIN
+#ifdef LED7_IS_PRESENT
     LED_INIT(7);
 #endif
 }