ARM: meson: serial: convert iounmap to devm_iounmap

The function meson_uart_release_port() inappropriately try to
iounmap() a resource managed by devm_ioremap_nocache().
The function meson_uart_release_port() maybe called by uart_ioctl()
that means meson_uart_release_port() is not called from within a
probe or remove function, for safety, I convert iounmap() to
devm_iounmap().
Signed-off-by: Firo Yang <firogm@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/meson_uart.c

@@ -370,7 +370,7 @@ static int meson_uart_verify_port(struct uart_port *port,
 static void meson_uart_release_port(struct uart_port *port)
 {
 	if (port->flags & UPF_IOREMAP) {
-		iounmap(port->membase);
+		devm_iounmap(port->dev, port->membase);
 		port->membase = NULL;
 	}
 }