Staging: IIO: DDS: AD9833 / AD9834 driver

Changes since RFC/v1:
IIO: Apply list review feedback

Apply list review feedback:
	Rename attributes to fit IIO convention used in other drivers.
	Fix typos.
	Provide ddsX_out_enable as opposed to ddsX_out_disable.
	Use proper __devexit marking.
	Use strict_strtoul() to avoid negatives.

Changes since v2:
IIO: ad9834.c: Apply more list review feedback

	Update use of dds convenience macros.
	Fix tabbing.
	Remove superfluous brackets.
	Keep output disabled after probe.
	Remove unnecessary code.

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