serial: qcom-geni: fix DMA mapping leak on shutdown

Fix what appears to be a copy-paste error that can lead to a leaked DMA
mapping on close() and failure to restart TX after the port is reopened.

Note that rx_dma_addr is generally NULL when
qcom_geni_serial_stop_tx_dma() is called as part of shutdown() (but
tx_dma_addr need not be).

Fixes: 2aaa43c ("tty: serial: qcom-geni-serial: add support for serial engine DMA")
Cc: stable <[email protected]>
Cc: Bartosz Golaszewski <[email protected]>
Signed-off-by: Johan Hovold <[email protected]>
Reviewed-by: Douglas Anderson <[email protected]>
Reviewed-by: Srinivas Kandagatla <[email protected]>
Tested-by: Srinivas Kandagatla <[email protected]>
Reviewed-by: Andrew Halaney <[email protected]>
Tested-by: Andrew Halaney <[email protected]> # sa8540p-ride
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: jhovold

drivers/tty/serial/qcom_geni_serial.c

@@ -596,7 +596,7 @@ static void qcom_geni_serial_stop_tx_dma(struct uart_port *uport)
 	if (!qcom_geni_serial_main_active(uport))
 		return;
 
-	if (port->rx_dma_addr) {
+	if (port->tx_dma_addr) {
 		geni_se_tx_dma_unprep(&port->se, port->tx_dma_addr,
 				      port->tx_remaining);
 		port->tx_dma_addr = 0;