Sorry all, this one is very invasive, though the driver changes are
just trivial interface fixes. Not all done yet.

V2 - bring the sca3000 with us.
V3 - fix ade7758 bugs in conversion.
V4 - add ad5933
Signed-off-by: Jonathan Cameron <jic23@cam.ac.uk>
Acked-by: Michael Hennerich <michael.hennerich@analog.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>