dmaengine: pl330: Clear callback_result for re-used descs

The pl330 driver re-uses DMA descriptors rather than reallocating
them each time. At present, upon re-use the .callback member is
cleared, but .callback result is not. This causes problems where a
consuming driver sets the .callback_result for some submissions but
not for others, as eventually the function is invoked erronously.

Clear .callback_result along with .callback
Signed-off-by: Daniel Scally <dan.scally@ideasonboard.com>
Link: https://lore.kernel.org/r/20240118112959.1027471-1-dan.scally@ideasonboard.comSigned-off-by: Vinod Koul <vkoul@kernel.org>

drivers/dma/pl330.c

@@ -2588,6 +2588,7 @@ static struct dma_pl330_desc *pluck_desc(struct list_head *pool,
 
 		desc->status = PREP;
 		desc->txd.callback = NULL;
+		desc->txd.callback_result = NULL;
 	}
 
 	spin_unlock_irqrestore(lock, flags);