iio: imu: inv_icm45600: fix temperature offset reporting

iio: imu: inv_icm45600: fix temperature offset reporting

Correct temperature computation is (raw + offset) * scale and not
apply scale and offset afterward.
Fix temperature offset reporting to the correct value and update
commentaries for the new computation.

Fixes: 27e072bc34d1 ("iio: imu: inv_icm45600: add IMU IIO gyroscope device")
Signed-off-by: Jean-Baptiste Maneyrol <jean-baptiste.maneyrol@tdk.com>
Cc: stable@vger.kernel.org
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>