iio: adc: aspeed: use devm_platform_ioremap_resource

Reduces boilerplate.

Identified by: Coccinelle / coccicheck

CHECK   drivers/iio/adc/aspeed_adc.c
drivers/iio/adc/aspeed_adc.c:189:1-11: WARNING: Use devm_platform_ioremap_resource for data -> base

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Rick Altherr <raltherr@google.com>
Reviewed-by: Alexandru Ardelean <alexandru.ardelean@analog.com>