iio: stk8ba50: Use scan_type when processing raw data

Use channel definition as root of trust and replace constant
when reading elements directly using the raw sysfs attributes.

Signed-off-by: Gwendal Grignou <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jonathan Cameron <[e-mail]>

drivers/iio/accel/stk8ba50.c

···
 			mutex_unlock(&data->lock);
 			return -EINVAL;
 		}
-		*val = sign_extend32(ret >> STK8BA50_DATA_SHIFT, 9);
+		*val = sign_extend32(ret >> chan->scan_type.shift,
+				     chan->scan_type.realbits - 1);
 		stk8ba50_set_power(data, STK8BA50_MODE_SUSPEND);
 		mutex_unlock(&data->lock);
 		return IIO_VAL_INT;