staging: iio: adc: ad799x drop in_precision in favor of new in_type

-drop in_precision in favor of new in_type -
This also fixes the bug from the scan elements move (as a side effect)
-add sign and storagebits to struct ad799x_chip_info
-properly mask the results based on ad799x_chip_info:bits

staging: iio: adc: ad799x misc fixed per iio list review

remove new line
remove storagebits from struct ad799x_chip_info
use defined storagebits value for in_type

Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
Acked-by: Jonathan Cameron <jic23@cam.ac.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>