iio:buffer_cb: Add missing iio_buffer_init()

Make sure to properly initialize the IIO buffer data structure.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
diff --git a/drivers/iio/buffer_cb.c b/drivers/iio/buffer_cb.c
index 9d19ba7..415f3c6 100644
--- a/drivers/iio/buffer_cb.c
+++ b/drivers/iio/buffer_cb.c
@@ -41,6 +41,8 @@
 		goto error_ret;
 	}
 
+	iio_buffer_init(&cb_buff->buffer);
+
 	cb_buff->private = private;
 	cb_buff->cb = cb;
 	cb_buff->buffer.access = &iio_cb_access;