Remove mpu6050_scale from core_t by providing a sensor independent way

of determining a revision code.  Previously there was mpu6050 specific
code in cli.c (the status command).

Finally this commit has removed all non-serial port configuration
settings from core_t so that a future commit can refactor core_t to
reduce dependencies on serial port code.

In doing this I also noted from other source code that the MPU6050
accelerometer trim for some revisions appeared to be incorrectly set to
255 * 8 instead of 256 * 8.

src/flight_imu.c

@@ -3,6 +3,7 @@
 
 #include "common/maths.h"
 
+#include "sensors_gyro.h"
 #include "sensors_compass.h"
 
 #include "flight_common.h"