iio: adc: adi-axi-adc: Make use of dev_err_probe()

iio: adc: adi-axi-adc: Make use of dev_err_probe()

Be consistent and use dev_err_probe() as in all other places in the
.probe() path.

While at it, remove the line break in the version condition. Yes, it
goes over the 80 column limit but I do think the line break hurts
readability in this case. And use a struct device *dev helper for
neater code.

Signed-off-by: Nuno Sá <nuno.sa@analog.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>