UWB IMU returns wrong readings on some boards

[msplr]

Some of the UWB Rev 1.1 (8 out of 12) give wrong IMU readings (constant nonsense value and changing seemingly random values).

My guess is that either the IMU is broken or the driver is buggy (maybe some communication errors are not detected).

@antoinealb suggested to make use of the IMU selftest function during initialization to rule out hardware failure.