drivers: iio: imu: adis16475: generic computation for sample rate

Currently adis16475 supports a sample rate between 1900 and 2100 Hz.
This patch changes the setting of sample rate from hardcoded values to
a generic computation based on the internal clock frequency.
This is a preparatory patch for adding support for adis1657x family
devices which allow sample rates between 3900 and 4100 Hz.

Reviewed-by: Nuno Sa <nuno.sa@analog.com>
Signed-off-by: Ramona Gradinariu <ramona.bolboaca13@gmail.com>
Link: https://lore.kernel.org/r/20240527142618.275897-6-ramona.bolboaca13@gmail.com


Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>