iio: adc: at91_adc: merge at91_adc_probe_dt back in at91_adc_probe

at91_adc_probe_dt is now small enough to be merged back in at91_adc_probe.

Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Reviewed-by: Ludovic Desroches <ludovic.desroches@microchip.com>
Link: https://lore.kernel.org/r/20201128222818.1910764-8-alexandre.belloni@bootlin.com


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