iio:adc:ad7923: Align broken line to parenthesis

Get broken line aligned with parenthesis on upper line. Solves
checkpatch.pl's message:

CHECK: Alignment should match open parenthesis
Signed-off-by: Bárbara Fernandes <barbara.fernandes@usp.br>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>