serial: stm32: Use __maybe_unused instead of #if CONFIG_PM_SLEEP

Use __maybe_unused for power management related functionsinstead of

fixes: 270e5a74fe4c ("serial: stm32: add wakeup mechanism")
Signed-off-by: Erwan Le Ray <[e-mail]>

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

drivers/tty/serial/stm32-usart.c

···
 	.cons		= STM32_SERIAL_CONSOLE,
 };
 
-#ifdef CONFIG_PM_SLEEP
-static void stm32_serial_enable_wakeup(struct uart_port *port, bool enable)
+static void __maybe_unused stm32_serial_enable_wakeup(struct uart_port *port,
+						      bool enable)
 {
 	struct stm32_port *stm32_port = to_stm32_port(port);
 	struct stm32_usart_offsets *ofs = &stm32_port->info->ofs;
···
 	}
 }
 
-static int stm32_serial_suspend(struct device *dev)
+static int __maybe_unused stm32_serial_suspend(struct device *dev)
 {
 	struct uart_port *port = dev_get_drvdata(dev);
 
···
 	return 0;
 }
 
-static int stm32_serial_resume(struct device *dev)
+static int __maybe_unused stm32_serial_resume(struct device *dev)
 {
 	struct uart_port *port = dev_get_drvdata(dev);
 
···
 
 	return uart_resume_port(&stm32_usart_driver, port);
 }
-#endif /* CONFIG_PM_SLEEP */
 
 static int __maybe_unused stm32_serial_runtime_suspend(struct device *dev)
 {