iio: adc: exynos: use devm_platform_ioremap_resource

Reduce local boilerplate.
Identified by coccinelle
drivers/iio/adc/exynos_adc.c:792:1-11: WARNING: Use devm_platform_ioremap_resource for info -> regs

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Chanwoo Choi <cw00.choi@samsung.com>