iio: ti-ads1015: Remove shift variable ads1015_read_raw

By using scan_type.realbits when processing raw data,
we use scan_type.shit only once, thus we don't need to define a local
variable for it anymore.

Signed-off-by: Gwendal Grignou <gwendal@chromium.org>
Link: https://lore.kernel.org/r/20211104082413.3681212-12-gwendal@chromium.org


Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>