dma: amba-pl08x: use vchan_dma_desc_free_list

vchan_dma_desc_free_list() iterates through each virt_dma_desc in the
specified list_head and calls vchan->desc_free().

We can use it instead of repeated execution of pl08x_desc_free() for each
virt_dma_desc in the list_head.  Because vchan->desc_free callback is set
as pl08x_desc_free() for amba-pl08x driver.
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Cc: Vinod Koul <vinod.koul@intel.com>
Cc: Dan Williams <djbw@fb.com>
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>

drivers/dma/amba-pl08x.c

@@ -1096,15 +1096,9 @@ static void pl08x_free_txd_list(struct pl08x_driver_data *pl08x,
 				struct pl08x_dma_chan *plchan)
 {
 	LIST_HEAD(head);
-	struct pl08x_txd *txd;
 
 	vchan_get_all_descriptors(&plchan->vc, &head);
-
-	while (!list_empty(&head)) {
-		txd = list_first_entry(&head, struct pl08x_txd, vd.node);
-		list_del(&txd->vd.node);
-		pl08x_desc_free(&txd->vd);
-	}
+	vchan_dma_desc_free_list(&plchan->vc, &head);
 }
 
 /*