iio:gyro: Add support for the ADIS16136 gyroscope

This patch adds support for the ADIS16133, ADIS16135, ADIS16136 single channel
gyroscopes. The main difference between them is the sensor precision.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>