Remove include <log.h> from defines.h

The reason for this is that log.h includes drv_hrt.h which sucks in
half the project's include files with it, which causes strange build
issues

platforms/common/px4_work_queue/ScheduledWorkItem.cpp

@@ -31,6 +31,7 @@
  *
  ****************************************************************************/
 
+#include <px4_platform_common/log.h>
 #include <px4_platform_common/px4_work_queue/ScheduledWorkItem.hpp>
 
 namespace px4