serial: sifive: Declare PM operations as static

They are only used within this file, so they should have static linkage.
Signed-off-by: Samuel Holland <samuel.holland@sifive.com>
Link: https://lore.kernel.org/r/20231113023122.1185407-1-samuel.holland@sifive.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/sifive.c

@@ -1031,7 +1031,7 @@ static int sifive_serial_resume(struct device *dev)
 	return uart_resume_port(&sifive_serial_uart_driver, &ssp->port);
 }
 
-DEFINE_SIMPLE_DEV_PM_OPS(sifive_uart_pm_ops, sifive_serial_suspend,
+static DEFINE_SIMPLE_DEV_PM_OPS(sifive_uart_pm_ops, sifive_serial_suspend,
 				sifive_serial_resume);
 
 static const struct of_device_id sifive_serial_of_match[] = {