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 <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/tty/serial/fsl_lpuart.c

···
 	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;
···
 	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));
···
 
 	return 0;
 }
-#endif
 
 static SIMPLE_DEV_PM_OPS(lpuart_pm_ops, lpuart_suspend, lpuart_resume);