staging:iio: Do not use bitmasks for channel info addresses

Currently the iio framework uses bitmasks for the address field of channel info
attributes. This is for historical reasons and no longer required since it will
only ever query a single info attribute at once. This patch changes the code to
use the non-shifted iio_chan_info_enum values for the info attribute address.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@cam.ac.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>