Reduces local boilerplate.
Found by coccinelle:

drivers/iio/adc/cc10001_adc.c:344:1-18: WARNING: Use devm_platform_ioremap_resource for adc_dev -> reg_base
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Cc: Naidu Tellapati <naidu.tellapati@imgtec.com>