serial: pch_uart: fix compilation warning

Function wait_for_xmitr is invoked only on functions that either depend
on CONFIG_CONSOLE_POLL or CONFIG_SERIAL_PCH_UART_CONSOLE.

This patch fixes the following warning:

drivers/tty/serial/pch_uart.c:1504:13: warning: ‘wait_for_xmitr’ defined but not used [-Wunused-function]
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/pch_uart.c

@@ -1524,6 +1524,7 @@ static int pch_uart_verify_port(struct uart_port *port,
 	return 0;
 }
 
+#if defined(CONFIG_CONSOLE_POLL) || defined(CONFIG_SERIAL_PCH_UART_CONSOLE)
 /*
  *	Wait for transmitter & holding register to empty
  */
@@ -1554,6 +1555,7 @@ static void wait_for_xmitr(struct eg20t_port *up, int bits)
 		}
 	}
 }
+#endif /* CONFIG_CONSOLE_POLL || CONFIG_SERIAL_PCH_UART_CONSOLE */
 
 #ifdef CONFIG_CONSOLE_POLL
 /*