iio: adc: aspeed: Simplify probe() with local 'dev' and 'np'

iio: adc: aspeed: Simplify probe() with local 'dev' and 'np'

Simplify the probe function by using local 'dev' and 'np' variables
instead of full pointer dereferences.  This makes several lines shorter,
which allows to avoid wrapping making code more readable.  While
touching the return line, simplify by avoiding unnecessary 'ret'
assignment.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>