iio:dac:ad5593r: Drop of_match_ptr and ACPI_PTR protections.

iio:dac:ad5593r: Drop of_match_ptr and ACPI_PTR protections.

These result in a very small reduction in driver size, but at the
cost of more complex build and slightly harder to read code.
In the case of of_match_ptr it also prevents use of PRP0001
ACPI based identification.  In this particular case we have
a valid ACPI/PNP ID that I am assuming was issued by Analog
Devices.  That should be used in preference to PRP0001 but doesn't
mean we should prevent that route.

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Michael Hennerich <michael.hennerich@analog.com>
Cc: Lars-Peter Clausen <lars@metafoo.de>
Link: https://lore.kernel.org/r/20200910173242.621168-12-jic23@kernel.org