iio: ep93xx: remove redundant return value check of platform_get_resource()

Remove unneeded error handling on the result of a call
to platform_get_resource() when the value is passed to
devm_ioremap_resource().

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