add DigitalIO.h for SOFTSPI in MQTTGateway.ino

Author: Marcelo Aquino

libraries/MySensors/examples/MQTTGateway/MQTTGateway.ino

@@ -56,6 +56,7 @@ http://forum.mysensors.org/topic/303/mqtt-broker-gateway
 
 */
 
+#include <DigitalIO.h>
 #include <SPI.h>
 #include <MySensor.h>
 #include <MyMQTT.h>
@@ -130,7 +131,6 @@ void writeEthernet(const char *writeBuffer, uint8_t *writeSize) {
   server.write((const uint8_t *)writeBuffer, *writeSize);
 }
 
-
 int main(void) {
   init();
   Ethernet.begin(TCP_MAC, TCP_IP);