iio: magnetometer: yas530: Correct temperature handling

iio: magnetometer: yas530: Correct temperature handling

The raw temperature value is a number of counts from a certain starting
point. The resolution of the temperature counts is different for the YAS
variants.

Temperature compensation for YAS532 version AC seems to be handled differently.
It uses the deviation from 20 degree Celsius [1] whereas YAS530 and older
versions of YAS532 apply solely the t value as a multiplier [2][3].

In funtion yas5xx_read_raw(), add case IIO_CHAN_INFO_PROCESSED. Remove scale
of temperature as this isn't applied.

Additionally correct sign of temperature channel in iio_chan_spec. It's already
defined that way in the yas5xx_get_measure() function.

[1] https://github.com/msm8916-mainline/android_kernel_qcom_msm8916/blob/GT-I9195I/drivers/iio/magnetometer/yas_mag_drv-yas532.c#L442
[2] https://github.com/NovaFusion/android_kernel_samsung_golden/blob/cm-12.1/drivers/sensor/compass/yas_mag_driver-yas530.c#L881-L883
[3] https://github.com/LineageOS/android_kernel_samsung_msm8930-common/blob/lineage-18.1/drivers/sensors/geomagnetic/yas_mag_driver-yas53x.c#L856-L858

Signed-off-by: Jakob Hauser <jahau@rocketmail.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/eb45f328c7a81eb622c6a8cfc5c468ea58bbdace.1660337264.git.jahau@rocketmail.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>