serial: pxa2xx: mark PM functions as __maybe_unused

The fresh new serial driver for pxa produces warnings when
CONFIG_PM_SLEEP is disabled:

drivers/tty/serial/8250/8250_pxa.c:50:12: error: 'serial_pxa_resume' defined but not used [-Werror=unused-function]
drivers/tty/serial/8250/8250_pxa.c:41:12: error: 'serial_pxa_suspend' defined but not used [-Werror=unused-function]

This removes the #ifdef around the two functions and instead marks both
as __maybe_unused, which is more robust and avoids the warning.

Fixes: ab28f51c ("serial: rewrite pxa2xx-uart to use 8250_core")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/8250/8250_pxa.c

@@ -37,8 +37,7 @@ struct pxa8250_data {
 	struct clk		*clk;
 };
 
-#ifdef CONFIG_PM
-static int serial_pxa_suspend(struct device *dev)
+static int __maybe_unused serial_pxa_suspend(struct device *dev)
 {
 	struct pxa8250_data *data = dev_get_drvdata(dev);
 
@@ -47,7 +46,7 @@ static int serial_pxa_suspend(struct device *dev)
 	return 0;
 }
 
-static int serial_pxa_resume(struct device *dev)
+static int __maybe_unused serial_pxa_resume(struct device *dev)
 {
 	struct pxa8250_data *data = dev_get_drvdata(dev);
 
@@ -55,7 +54,6 @@ static int serial_pxa_resume(struct device *dev)
 
 	return 0;
 }
-#endif
 
 static const struct dev_pm_ops serial_pxa_pm_ops = {
 	SET_SYSTEM_SLEEP_PM_OPS(serial_pxa_suspend, serial_pxa_resume)