use regulated time for frequency noise to avoid spurious harmonics
SITL sensors must be true separate instances
don't compile in FFT structures if DSP disabled
This allows each sensor to be uniquely identified in the system by using
either the index inside the backend or for those that use the Device
interface, to use the bus type, location, and device id.
We leave 16-bit for each sensor to be able to change its own
identification in future, which allows them to be changed in an
incompatible manner forcing a re-calibration.
We only leave the parameter there for backward-compatibility. However
product id on the inertial sensor is not much useful since it's only
kept for the first instance.
A better implementation per-gyro and per-accel is needed in order to
avoid problems with sensors taking the offsets configured for another
sensor.
RC_Channel: To nullptr from NULL.
AC_Fence: To nullptr from NULL.
AC_Avoidance: To nullptr from NULL.
AC_PrecLand: To nullptr from NULL.
DataFlash: To nullptr from NULL.
SITL: To nullptr from NULL.
GCS_MAVLink: To nullptr from NULL.
DataFlash: To nullptr from NULL.
AP_Compass: To nullptr from NULL.
Global: To nullptr from NULL.
Global: To nullptr from NULL.