serial: imx: Fix the CTS_B polarity in RS485 mode

When userspace passes the SER_RS485_RTS_ON_SEND flag it means that the
CTS_B pin should go to logic level high before the transmission begins.

CTS_B goes to logic level high when both CTSC and CTS bits are cleared.

When userspace passes the SER_RS485_RTS_AFTER_SEND flag it means that the
CTS_B pin should go to logic level low after the transmission finishes.

CTS_B goes to logic level low when CTSC bit is cleared and CTS bit is set.

So fix the CTS_B polarity logic.
Signed-off-by: NFabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/imx.c

@@ -336,15 +336,15 @@ static void imx_port_ucrs_restore(struct uart_port *port,
 
 static void imx_port_rts_active(struct imx_port *sport, unsigned long *ucr2)
 {
-	*ucr2 &= ~UCR2_CTSC;
-	*ucr2 |= UCR2_CTS;
+	*ucr2 &= ~(UCR2_CTSC | UCR2_CTS);
 
 	mctrl_gpio_set(sport->gpios, sport->port.mctrl | TIOCM_RTS);
 }
 
 static void imx_port_rts_inactive(struct imx_port *sport, unsigned long *ucr2)
 {
-	*ucr2 &= ~(UCR2_CTSC | UCR2_CTS);
+	*ucr2 &= ~UCR2_CTSC;
+	*ucr2 |= UCR2_CTS;
 
 	mctrl_gpio_set(sport->gpios, sport->port.mctrl & ~TIOCM_RTS);
 }