staging: iio: adc: ad7192: Re-indent enum labels

Re-indent enum labels as per coding style guidelines. Problem
detected by checkpatch script.

Signed-off-by: Deepak R Varma <mh12gx2825@gmail.com>
Link: https://lore.kernel.org/r/5c6bef6462d135b748f58f8c2645c60234482f52.1584904896.git.mh12gx2825@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>