iio: adc: ingenic: remove redundant dev_err call in ingenic_adc_probe()

There is a error message within devm_ioremap_resource
already, so remove the dev_err call to avoid redundant
error message.

Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>