serial: fix enable_irq_wake/disable_irq_wake imbalance in serial_core.c

enable_irq_wake() and disable_irq_wake() need to be balanced.  However,
serial_core.c calls these for different conditions during the suspend and
resume functions...

This is causing a regular WARN_ON() as found at
http://www.kerneloops.org/search.php?search=set_irq_wake

This patch makes the conditions for triggering the _wake enable/disable
sequence identical.
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/serial/serial_core.c

@@ -2054,6 +2054,8 @@ int uart_suspend_port(struct uart_driver *drv, struct uart_port *port)
 int uart_resume_port(struct uart_driver *drv, struct uart_port *port)
 {
 	struct uart_state *state = drv->state + port->line;
+	struct device *tty_dev;
+	struct uart_match match = {port, drv};
 
 	mutex_lock(&state->mutex);
 
@@ -2063,7 +2065,8 @@ int uart_resume_port(struct uart_driver *drv, struct uart_port *port)
 		return 0;
 	}
 
-	if (!port->suspended) {
+	tty_dev = device_find_child(port->dev, &match, serial_match_port);
+	if (!port->suspended && device_may_wakeup(tty_dev)) {
 		disable_irq_wake(port->irq);
 		mutex_unlock(&state->mutex);
 		return 0;