Adds missing includes

Author: Veijo Pesonen

ESP8266/ESP8266.h

@@ -18,6 +18,7 @@
 #define ESP8266_H
 
 #include "ATCmdParser.h"
+#include "Mutex.h"
 #include "nsapi_types.h"
 #include "rtos.h"
 

ESP8266Interface.h

@@ -18,8 +18,15 @@
 #define ESP8266_INTERFACE_H
 
 #include "mbed.h"
-#include "ESP8266.h"
 
+#include "Callback.h"
+#include "netsocket/nsapi_types.h"
+#include "netsocket/NetworkInterface.h"
+#include "netsocket/NetworkStack.h"
+#include "netsocket/WiFiAccessPoint.h"
+#include "netsocket/WiFiInterface.h"
+
+#include "ESP8266.h"
 
 #define ESP8266_SOCKET_COUNT 5