staging:iio: Reorder channel type strings to match the iio.h enums.

This makes comparison between the iio_chan_type_name_spec_shared strings
and the iio_chan_type enums easier.

Signed-off-by: Bryan Freed <bfreed@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>