iio: imu: adis16480: Add support for ADIS1649x family of devices

The ADIS16495 and ADIS16497 are inertial systems that include a triaxis
gyroscope and a triaxis accelerometer. The serial peripheral interface
(SPI) provide a simple interface for data collection and configuration
control. The devices are similar to ADIS16475, ADIS16480, ADIS16485 and
ADIS16488, the main differences are highlighted below:

* The temperature data scale is 0.00565 C/LSB for ADIS16475 and ADIS1648x
  devices, while for ADIS1649x 0.0125 C/LSB.

* ADIS1649x devices support different gyroscope measurement ranges which
  are dependent on the dash number (-1, -2, -3), see Table 24 in the
  ADIS16495 datasheet. However, the ADIS16497 gyroscopes have the same
  scale as ADIS16495.

* ADIS16495 devices support the acceleration maximum range of 8g, while
  ADIS16497 devices go up to 40g.

* The internal clock for ADIS1649x devices is 4.25 kSPS. The sampling
  frequency is calculated by applying a decimation rate which can take a
  maximum value of 4250.

* ADIS1649x devices support different default filter frequencies.

Datasheets:
Link: https://www.analog.com/media/en/technical-documentation/data-sheets/adis16495.pdf
Link: https://www.analog.com/media/en/technical-documentation/data-sheets/adis16497.pdf



Signed-off-by: Stefan Popa <stefan.popa@analog.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>