tty: serial: fsl_lpuart: Use __maybe_unused instead of #if CONFIG_PM_SLEEP

Use __maybe_unused for power management related functions to simplify
the code.
Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Link: https://lore.kernel.org/r/1589547481-25932-1-git-send-email-Anson.Huang@nxp.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/fsl_lpuart.c

@@ -2665,8 +2665,7 @@ static int lpuart_remove(struct platform_device *pdev)
 	return 0;
 }
 
-#ifdef CONFIG_PM_SLEEP
-static int lpuart_suspend(struct device *dev)
+static int __maybe_unused lpuart_suspend(struct device *dev)
 {
 	struct lpuart_port *sport = dev_get_drvdata(dev);
 	unsigned long temp;
@@ -2724,7 +2723,7 @@ static int lpuart_suspend(struct device *dev)
 	return 0;
 }
 
-static int lpuart_resume(struct device *dev)
+static int __maybe_unused lpuart_resume(struct device *dev)
 {
 	struct lpuart_port *sport = dev_get_drvdata(dev);
 	bool irq_wake = irqd_is_wakeup_set(irq_get_irq_data(sport->port.irq));
@@ -2755,7 +2754,6 @@ static int lpuart_resume(struct device *dev)
 
 	return 0;
 }
-#endif
 
 static SIMPLE_DEV_PM_OPS(lpuart_pm_ops, lpuart_suspend, lpuart_resume);