DMP code commented in the AP_InertialSensor_MPU9150 driver.

The Invensense Digital Motion Processor embedded on the MPU9150 won't
be used because it's intented only for slow moving vehicles that don't
have significant inertial forces (not the case with UAVs).

ardupilot uses its own attitude estimators that only required
the raw sensor values.
Add 400 Hz sampling freq