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

src/drivers/magnetometer/hmc5883/HMC5883.hpp

@@ -35,6 +35,7 @@
 
 #include <px4_platform_common/px4_config.h>
 #include <px4_platform_common/defines.h>
+#include <px4_platform_common/log.h>
 #include <px4_platform_common/time.h>
 #include <drivers/device/i2c.h>
 #include <px4_platform_common/i2c_spi_buses.h>

src/drivers/magnetometer/hmc5883/hmc5883_i2c.cpp

@@ -38,6 +38,7 @@
  */
 
 #include <px4_platform_common/px4_config.h>
+#include <px4_platform_common/log.h>
 #include <drivers/device/i2c.h>
 
 #include "hmc5883.h"

src/drivers/magnetometer/hmc5883/hmc5883_spi.cpp

@@ -38,6 +38,7 @@
  */
 
 #include <px4_platform_common/px4_config.h>
+#include <px4_platform_common/log.h>
 #include <drivers/device/spi.h>
 
 #include "hmc5883.h"