dmatest: fix automatic buffer unmap type

The dmatest code relies on the DMAEngine API to automatically call
dma_unmap_single() on src buffers. The flags it passes are incorrect,
fix them.
Signed-off-by: NIra W. Snyder <iws@ovro.caltech.edu>
Signed-off-by: NDan Williams <dan.j.williams@intel.com>

drivers/dma/dmatest.c

@@ -285,7 +285,12 @@ static int dmatest_func(void *data)
 
 	set_user_nice(current, 10);
 
-	flags = DMA_CTRL_ACK | DMA_COMPL_SKIP_DEST_UNMAP | DMA_PREP_INTERRUPT;
+	/*
+	 * src buffers are freed by the DMAEngine code with dma_unmap_single()
+	 * dst buffers are freed by ourselves below
+	 */
+	flags = DMA_CTRL_ACK | DMA_PREP_INTERRUPT
+	      | DMA_COMPL_SKIP_DEST_UNMAP | DMA_COMPL_SRC_UNMAP_SINGLE;
 
 	while (!kthread_should_stop()
 	       && !(iterations && total_tests >= iterations)) {