iio: adc: ti_am335x_adc: avoid double free of buffer.

The driver is missing the iio_buffer_attach() call. As such it will attempt
to free the buffer twice on removal.

Introduced in commit 9e69c9 ("iio: Add reference counting for buffers").
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Reported-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/adc/ti_am335x_adc.c

@@ -229,12 +229,15 @@ static int tiadc_iio_buffered_hardware_setup(struct iio_dev *indio_dev,
 	unsigned long flags,
 	const struct iio_buffer_setup_ops *setup_ops)
 {
+	struct iio_buffer *buffer;
 	int ret;
 
-	indio_dev->buffer = iio_kfifo_allocate(indio_dev);
-	if (!indio_dev->buffer)
+	buffer = iio_kfifo_allocate(indio_dev);
+	if (!buffer)
 		return -ENOMEM;
 
+	iio_device_attach_buffer(indio_dev, buffer);
+
 	ret = request_threaded_irq(irq,	pollfunc_th, pollfunc_bh,
 				flags, indio_dev->name, indio_dev);
 	if (ret)