Fix missing DDR initialisation for led driver

boards/nano.mk

@@ -1,6 +1,7 @@
 MCU_TARGET = atmega328p
 MCU_FREQ = 16000000UL
-CPPFLAGS += -DLED_PORT=PORTB -DLED_PIN=5
+
+CPPFLAGS += -DLED_DDR=DDRB -DLED_PORT=PORTB -DLED_PIN=5
 
 AVRDUDE_TYPE = arduino
 AVRDUDE_TTY = /dev/ttyUSB0

drivers/led.c

@@ -1,6 +1,10 @@
 #include "led.h"
 #include <avr/io.h>
 
+void __attribute__ ((naked)) __attribute__ ((section (".init5"))) led_init() {
+	LED_DDR |= (1 << LED_PIN);
+}
+
 void led(uint8_t on) {
 	if (on) {
 		LED_PORT |= (1 << LED_PIN);