iio: buffer-dma: Use ARRAY_SIZE in for loop range

Use the ARRAY_SIZE macro in the for loops that access queue->fileio.blocks.
Macro is already used in a couple of places where this access occurs,
but range was hardcoded in these locations.
Signed-off-by: NPhil Reid <preid@electromag.com.au>
Acked-by: NLars-Peter Clausen <lars@metafoo.de>
Signed-off-by: NJonathan Cameron <jic23@kernel.org>

drivers/iio/buffer/industrialio-buffer-dma.c

@@ -305,7 +305,7 @@ int iio_dma_buffer_request_update(struct iio_buffer *buffer)
 	queue->fileio.active_block = NULL;
 
 	spin_lock_irq(&queue->list_lock);
-	for (i = 0; i < 2; i++) {
+	for (i = 0; i < ARRAY_SIZE(queue->fileio.blocks); i++) {
 		block = queue->fileio.blocks[i];
 
 		/* If we can't re-use it free it */
@@ -323,7 +323,7 @@ int iio_dma_buffer_request_update(struct iio_buffer *buffer)
 
 	INIT_LIST_HEAD(&queue->incoming);
 
-	for (i = 0; i < 2; i++) {
+	for (i = 0; i < ARRAY_SIZE(queue->fileio.blocks); i++) {
 		if (queue->fileio.blocks[i]) {
 			block = queue->fileio.blocks[i];
 			if (block->state == IIO_BLOCK_STATE_DEAD) {