iio: adc: at91-sama5d2_adc: Use devm_platform_get_and_ioremap_resource()

Make use of devm_platform_get_and_ioremap_resource() provided by
driver core platform instead of duplicated analogue.

Signed-off-by: Wang ShaoBo <bobo.shaobowang@huawei.com>
Link: https://lore.kernel.org/r/20200918082837.32610-1-bobo.shaobowang@huawei.com


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