tty: serial: imx: add pinctrl sleep/default mode switch for suspend

On some i.MX SoCs' low power mode, such as i.MX7D's LPSR(low power
state retention), UART iomux settings will be lost, need to add
pinctrl sleep/default mode switch during suspend/resume to make
sure UART iomux settings are correct after resume.
Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/imx.c

@@ -24,6 +24,7 @@
 #include <linux/serial.h>
 #include <linux/clk.h>
 #include <linux/delay.h>
+#include <linux/pinctrl/consumer.h>
 #include <linux/rational.h>
 #include <linux/slab.h>
 #include <linux/of.h>
@@ -2444,6 +2445,8 @@ static int imx_uart_suspend_noirq(struct device *dev)
 
 	clk_disable(sport->clk_ipg);
 
+	pinctrl_pm_select_sleep_state(dev);
+
 	return 0;
 }
 
@@ -2452,6 +2455,8 @@ static int imx_uart_resume_noirq(struct device *dev)
 	struct imx_port *sport = dev_get_drvdata(dev);
 	int ret;
 
+	pinctrl_pm_select_default_state(dev);
+
 	ret = clk_enable(sport->clk_ipg);
 	if (ret)
 		return ret;