iio: adc: at91_adc: remove at91_adc_ids

The driver is DT only since commit ead1c9f3 ("iio: adc: at91_adc:
remove platform data and move defs in driver file"). Remove the leftover
platform_device_id array.

Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20201128222818.1910764-2-alexandre.belloni@bootlin.com


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