px4.h: remove this include, causes compile problems on GCC 6.1.0

It causes problems because it includes px4_nodehandle.h which in turn
includes <functional>, and this is not available on NuttX

src/modules/logger/log_writer_file.h

@@ -33,7 +33,7 @@
 
 #pragma once
 
-#include <px4.h>
+#include <px4_defines.h>
 #include <stdint.h>
 #include <pthread.h>
 #include <drivers/drv_hrt.h>

src/modules/logger/logger.h

@@ -35,7 +35,7 @@
 
 #include "log_writer.h"
 #include "array.h"
-#include <px4.h>
+#include <px4_defines.h>
 #include <drivers/drv_hrt.h>
 #include <uORB/Subscription.hpp>
 #include <version/version.h>