USB: serial: sierra: fix potential deadlock at close

The portdata spinlock can be taken in interrupt context (via
sierra_outdat_callback()).
Disable interrupts when taking the portdata spinlock when discarding
deferred URBs during close to prevent a possible deadlock.

Fixes: 014333f77c0b ("USB: sierra: fix urb and memory leak on disconnect")
Cc: stable <[e-mail]>
Signed-off-by: John Ogness <[e-mail]>
Signed-off-by: Sebastian Andrzej Siewior <[e-mail]>
[ johan: amend commit message and add fixes and stable tags ]
Signed-off-by: Johan Hovold <[e-mail]>

drivers/usb/serial/sierra.c

···
 		kfree(urb->transfer_buffer);
 		usb_free_urb(urb);
 		usb_autopm_put_interface_async(serial->interface);
-		spin_lock(&portdata->lock);
+		spin_lock_irq(&portdata->lock);
 		portdata->outstanding_urbs--;
-		spin_unlock(&portdata->lock);
+		spin_unlock_irq(&portdata->lock);
 	}
 
 	sierra_stop_rx_urbs(port);