staging: iio: remove odd structure definition.

I've no idea where this came from!
Also fixed form -> from in comment

Signed-off-by: Jonathan Cameron <jic23@cam.ac.uk>
Acked-by: Manuel Stahl <manuel.stahl@iis.fraunhofer.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>