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/posix/src/px4/common/px4_sem.cpp

@@ -38,6 +38,7 @@
  */
 
 #include <px4_platform_common/defines.h>
+#include <px4_platform_common/log.h>
 #include <px4_platform_common/workqueue.h>
 #include <px4_platform_common/time.h>
 #include <stdint.h>