[driver] Bosch Sensortec BMI270 IMU

[hshose]

BMI270 IMU driver.

• example with interrupts i2c
• example with interrupts spi
• fifo buffer example
• component retrim ("CRT") calibration example. There is a bug when writing to the devices non-volatile memory (only 14-ish write cycles per datasheet anyways), so the example is set up to allow for the stm32 to retrieve the retrim values, e.g., to store them in the flash_reserved section. @joelsa has more experience with the calibration. I messed around with the vendors offset calibration routine (this calibrates for constant bias and is called "FOC") and applying in the imu's registers, but this was pretty buggy. I therefore recommend to do bias calibration in software (e.g., from an average over motionless values).

Also thanks and credits to @joelsa for explaining the CRT issues to me and building the breakout board I used for testing 🎉

[hshose]

rebased fixup commits.

All I2C examples tested in hardware. Unfortunately, I don't have a breakout board to test the SPI example.

[hshose]

@salkinium thank you for the review :-)