serial: imx: unmap sg in case of dmaengine_prep_slave_sg() failure

In case dmaengine_prep_slave_sg() fails, add the missing dma_unmap_sg().
Signed-off-by: Dirk Behme <dirk.behme@de.bosch.com>
Signed-off-by: Anton Bondarenko <anton_bondarenko@mentor.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/imx.c

@@ -558,6 +558,8 @@ static void imx_dma_tx(struct imx_port *sport)
 	desc = dmaengine_prep_slave_sg(chan, sgl, sport->dma_tx_nents,
 					DMA_MEM_TO_DEV, DMA_PREP_INTERRUPT);
 	if (!desc) {
+		dma_unmap_sg(dev, sgl, sport->dma_tx_nents,
+			     DMA_TO_DEVICE);
 		dev_err(dev, "We cannot prepare for the TX slave dma!\n");
 		return;
 	}
@@ -947,6 +949,7 @@ static int start_rx_dma(struct imx_port *sport)
 	desc = dmaengine_prep_slave_sg(chan, sgl, 1, DMA_DEV_TO_MEM,
 					DMA_PREP_INTERRUPT);
 	if (!desc) {
+		dma_unmap_sg(dev, sgl, 1, DMA_FROM_DEVICE);
 		dev_err(dev, "We cannot prepare for the RX slave dma!\n");
 		return -EINVAL;
 	}