serial: imx: Fix DCD reading

The USR2_DCDIN bit is tested for in register usr1. As the name
suggests the usr2 register should be used instead. This fixes
reading the Carrier detect status.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Fixes: 90ebc4838666 ("serial: imx: repair and complete handshaking")
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Cc: <stable@vger.kernel.org> # 4.5+
Reviewed-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/imx.c

@@ -763,12 +763,13 @@ static unsigned int imx_get_hwmctrl(struct imx_port *sport)
 {
 	unsigned int tmp = TIOCM_DSR;
 	unsigned usr1 = readl(sport->port.membase + USR1);
+	unsigned usr2 = readl(sport->port.membase + USR2);
 
 	if (usr1 & USR1_RTSS)
 		tmp |= TIOCM_CTS;
 
 	/* in DCE mode DCDIN is always 0 */
-	if (!(usr1 & USR2_DCDIN))
+	if (!(usr2 & USR2_DCDIN))
 		tmp |= TIOCM_CAR;
 
 	if (sport->dte_mode)