drm/omap: dmm_tiler: Use dmaengine_prep_dma_memcpy() for i878 workaround

Instead of dma_dev->device_prep_dma_memcpy() use the existing macro to
prepare the memcpy.
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190731094233.13890-2-peter.ujfalusi@ti.com

drivers/gpu/drm/omapdrm/omap_dmm_tiler.c

@@ -82,12 +82,11 @@ static const u32 reg[][4] = {
 
 static int dmm_dma_copy(struct dmm *dmm, dma_addr_t src, dma_addr_t dst)
 {
-	struct dma_device *dma_dev = dmm->wa_dma_chan->device;
 	struct dma_async_tx_descriptor *tx;
 	enum dma_status status;
 	dma_cookie_t cookie;
 
-	tx = dma_dev->device_prep_dma_memcpy(dmm->wa_dma_chan, dst, src, 4, 0);
+	tx = dmaengine_prep_dma_memcpy(dmm->wa_dma_chan, dst, src, 4, 0);
 	if (!tx) {
 		dev_err(dmm->dev, "Failed to prepare DMA memcpy\n");
 		return -EIO;