iio: humidity: hts221: Drop ACPI_PTR() usage

iio: humidity: hts221: Drop ACPI_PTR() usage

Avoiding unused variable warnings when using this macro adds
complexity that in simple cases like this one is not justified
for the small saving in data.

Switch include to mod_devicetable.h as that contains the only
ACPI specific definitions needed in this driver.

Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20231231183514.566609-11-jic23@kernel.org
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>