iio: gyro: Add driver support for ADXRS290

ADXRS290 is a high performance MEMS pitch and roll (dual-axis in-plane)
angular rate sensor (gyroscope) designed for use in stabilization
applications. It also features an internal temperature sensor and
programmable high-pass and low-pass filters.

Add support for ADXRS290 in direct-access mode for now.

Datasheet: https://www.analog.com/media/en/technical-documentation/data-sheets/ADXRS290.pdf


Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Nishant Malpani <nish.malpani25@gmail.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>