serial: imx: simplify some conditions related to dma

Neither .dma_is_txing nor .dma_is_rxing can evaluate to true if
.dma_is_enabled evaluates to false:

The only function that sets .dma_is_txing to a non-zero value is
imx_dma_tx() which is only called if .dma_is_enabled is true. Same for
.dma_is_rxing and start_rx_dma(). And before .dma_is_enabled is set to 0
when imx_shutdown calls imx_disable_dma(), .dma_is_rxing and
.dma_is_txing are reset to zero before, too.

For this reason

	sport->dma_is_enabled && sport->dma_is_rxing

has the same value as

	sport->dma_is_rxing

which allows to simplify three if conditions.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/imx.c

@@ -413,7 +413,7 @@ static void imx_stop_tx(struct uart_port *port)
 	 * We are maybe in the SMP context, so if the DMA TX thread is running
 	 * on other cpu, we have to wait for it to finish.
 	 */
-	if (sport->dma_is_enabled && sport->dma_is_txing)
+	if (sport->dma_is_txing)
 		return;
 
 	temp = imx_uart_readl(sport, UCR1);
@@ -442,7 +442,7 @@ static void imx_stop_rx(struct uart_port *port)
 	struct imx_port *sport = (struct imx_port *)port;
 	unsigned long temp;
 
-	if (sport->dma_is_enabled && sport->dma_is_rxing) {
+	if (sport->dma_is_rxing) {
 		if (sport->port.suspended) {
 			dmaengine_terminate_all(sport->dma_chan_rx);
 			sport->dma_is_rxing = 0;
@@ -900,7 +900,7 @@ static unsigned int imx_tx_empty(struct uart_port *port)
 	ret = (imx_uart_readl(sport, USR2) & USR2_TXDC) ?  TIOCSER_TEMT : 0;
 
 	/* If the TX DMA is working, return 0. */
-	if (sport->dma_is_enabled && sport->dma_is_txing)
+	if (sport->dma_is_txing)
 		ret = 0;
 
 	return ret;