Staging: iio: cdc: Remove unused macros

Remove the macros since they are not used anywhere throughout the
kernel.

Signed-off-by: Shraddha Barke <shraddha.6596@gmail.com>
Reviewed-by: Daniel Baluta <daniel.baluta@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>