iio: pressure: dps310: simplify scale factor reading

Both functions `dps310_get_pres_precision` and
`dps310_get_temp_precision` provide the oversampling rate by calling the
`BIT()` macro. However, to look up the corresponding scale factor, we
need the register value itself. Currently, this is achieved by undoing
the calculation of the oversampling rate with `ilog2()`.

Simplify the two functions for getting the scale factor and directly
use the register content for the lookup.

Signed-off-by: Thomas Haemmerle <thomas.haemmerle@leica-geosystems.com>
Link: https://lore.kernel.org/r/20240415105030.1161770-5-thomas.haemmerle@leica-geosystems.com


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