iio:adc:ti_am335x_adc Fix buffered mode by identifying as software buffer.

Whilst this part has a hardware buffer, the identifcation that IIO cares
about is the userspace facing end.  It this case we push individual elements
from the hardware fifo into the software interface (specifically a kfifo)
rather than providing direct reads through to a hardware buffer
(as we still do in the sca3000 for example).

Technically the original specification as a hardware buffer could be
considered wrong, but it didn't matter until the patch listed below.

Result is that any attempt to enable the buffer will return -EINVAL

Fixes: 225d59ad ("iio: Specify supported modes for buffers")
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/adc/ti_am335x_adc.c

@@ -289,7 +289,7 @@ static int tiadc_iio_buffered_hardware_setup(struct iio_dev *indio_dev,
 		goto error_kfifo_free;
 
 	indio_dev->setup_ops = setup_ops;
-	indio_dev->modes |= INDIO_BUFFER_HARDWARE;
+	indio_dev->modes |= INDIO_BUFFER_SOFTWARE;
 
 	return 0;