staging:iio:resolver:ad2s90 ensure name is passed to iio_core.

Scraps the pointless name define and adds an id table.
It's not technically required in drivers with only one supported
part but it does make the probe code more consistent.

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>