iio: temperature: ltc2983: Make use of device properties

Convert the module to be property provider agnostic and allow
it to be used on non-OF platforms.

The conversion slightly changes the logic behind property reading for
the configuration values. Original code allocates just as much memory
as needed. Then for each separate 32- or 64-bit value it reads it from
the property and converts to a raw one which will be fed to the sensor.
In the new code we allocate the amount of memory needed to retrieve all
values at once from the property and then convert them as required.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Nuno Sá <nuno.sa@analog.com>
Tested-by: Nuno Sá <nuno.sa@analog.com>
Link: https://lore.kernel.org/r/20220307203606.87258-3-andriy.shevchenko@linux.intel.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>