iio: buffer-dma: Remove unused iio_buffer_block struct

This structure was never used anywhere, so it can safely be dropped.

It will later be re-introduced as a different structure in a
different header.
Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Reviewed-by: Alexandru Ardelean <ardeleanalex@gmail.com>
Link: https://lore.kernel.org/r/20211115141925.60164-3-paul@crapouillou.netSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

include/linux/iio/buffer-dma.h

@@ -17,11 +17,6 @@ struct iio_dma_buffer_queue;
 struct iio_dma_buffer_ops;
 struct device;
 
-struct iio_buffer_block {
-	u32 size;
-	u32 bytes_used;
-};
-
 /**
  * enum iio_block_state - State of a struct iio_dma_buffer_block
  * @IIO_BLOCK_STATE_DEQUEUED: Block is not queued