iio: cleanup iio/iio.h

indentation of parameter description,
fix parameter name (@dev -> @indio_dev) in comments,
IIO device info structure -> IIO device structure

Signed-off-by: Peter Meerwald <pmeerw@pmeerw.net>
Acked-by: Jonathan Cameron <jic23@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>