spi: support spi without dma channel to use can_dma()

For spi without dma channel and use can_dma(), it can
use master->dev for struct device.
Signed-off-by: Leilk Liu <leilk.liu@mediatek.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi.c

@@ -539,8 +539,15 @@ static int __spi_map_msg(struct spi_master *master, struct spi_message *msg)
 	if (!master->can_dma)
 		return 0;
 
-	tx_dev = master->dma_tx->device->dev;
-	rx_dev = master->dma_rx->device->dev;
+	if (master->dma_tx)
+		tx_dev = master->dma_tx->device->dev;
+	else
+		tx_dev = &master->dev;
+
+	if (master->dma_rx)
+		rx_dev = master->dma_rx->device->dev;
+	else
+		rx_dev = &master->dev;
 
 	list_for_each_entry(xfer, &msg->transfers, transfer_list) {
 		if (!master->can_dma(master, msg->spi, xfer))
@@ -579,8 +586,15 @@ static int __spi_unmap_msg(struct spi_master *master, struct spi_message *msg)
 	if (!master->cur_msg_mapped || !master->can_dma)
 		return 0;
 
-	tx_dev = master->dma_tx->device->dev;
-	rx_dev = master->dma_rx->device->dev;
+	if (master->dma_tx)
+		tx_dev = master->dma_tx->device->dev;
+	else
+		tx_dev = &master->dev;
+
+	if (master->dma_rx)
+		rx_dev = master->dma_rx->device->dev;
+	else
+		rx_dev = &master->dev;
 
 	list_for_each_entry(xfer, &msg->transfers, transfer_list) {
 		if (!master->can_dma(master, msg->spi, xfer))