iio: gyro: adxrs290: fix data signedness

Properly sign-extend the rate and temperature data.

Fixes: 2c8920ff ("iio: gyro: Add driver support for ADXRS290")
Signed-off-by: Kister Genesis Jimenez <kister.jimenez@analog.com>
Signed-off-by: Nuno Sá <nuno.sa@analog.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20211115104147.18669-1-nuno.sa@analog.com


Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>