iio: ep93xx: Remove redundant error printing in ep93xx_adc_probe()

iio: ep93xx: Remove redundant error printing in ep93xx_adc_probe()

When devm_ioremap_resource() fails, a clear enough error message will be
printed by its subfunction __devm_ioremap_resource(). The error
information contains the device name, failure cause, and possibly resource
information.

Therefore, remove the error printing here to simplify code and reduce the
binary size.

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>