serial: lantiq: Make UART's use as console selectable

Lantiq UART driver can be used for system console. Add changes to
make this driver's use as console selectable/configurable.

Signed-off-by: Rahul Tanwar <rahul.tanwar@linux.intel.com>
Link: https://lore.kernel.org/r/35f2d002ba1cb26192fe4d9b8cdab275300705bc.1589176044.git.rahul.tanwar@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/Kconfig

@@ -1037,10 +1037,17 @@ config SERIAL_LANTIQ
 	bool "Lantiq serial driver"
 	depends on (LANTIQ || X86) || COMPILE_TEST
 	select SERIAL_CORE
+	help
+	  Support for UART on Lantiq and Intel SoCs.
+
+config SERIAL_LANTIQ_CONSOLE
+	bool "Console on Lantiq UART"
+	depends on SERIAL_LANTIQ=y
 	select SERIAL_CORE_CONSOLE
 	select SERIAL_EARLYCON
 	help
-	  Support for console and UART on Lantiq SoCs.
+	  Select this option if you would like to use a Lantiq UART as the
+	  system console.
 
 config SERIAL_QE
 	tristate "Freescale QUICC Engine serial port support"

drivers/tty/serial/lantiq.c

@@ -597,6 +597,7 @@ static const struct uart_ops lqasc_pops = {
 	.verify_port =	lqasc_verify_port,
 };
 
+#ifdef CONFIG_SERIAL_LANTIQ_CONSOLE
 static void
 lqasc_console_putchar(struct uart_port *port, int ch)
 {
@@ -705,6 +706,14 @@ lqasc_serial_early_console_setup(struct earlycon_device *device,
 OF_EARLYCON_DECLARE(lantiq, "lantiq,asc", lqasc_serial_early_console_setup);
 OF_EARLYCON_DECLARE(lantiq, "intel,lgm-asc", lqasc_serial_early_console_setup);
 
+#define LANTIQ_SERIAL_CONSOLE	(&lqasc_console)
+
+#else
+
+#define LANTIQ_SERIAL_CONSOLE	NULL
+
+#endif /* CONFIG_SERIAL_LANTIQ_CONSOLE */
+
 static struct uart_driver lqasc_reg = {
 	.owner =	THIS_MODULE,
 	.driver_name =	DRVNAME,
@@ -712,7 +721,7 @@ static struct uart_driver lqasc_reg = {
 	.major =	0,
 	.minor =	0,
 	.nr =		MAXPORTS,
-	.cons =		&lqasc_console,
+	.cons =		LANTIQ_SERIAL_CONSOLE,
 };
 
 static int fetch_irq_lantiq(struct device *dev, struct ltq_uart_port *ltq_port)