[WATCHDOG] pcwd_usb.c: fix a NULL pointer dereference

The Coverity checker noted that this resulted in a NULL pointer
reference if we were coming from

        if (usb_pcwd == NULL) {
                printk(KERN_ERR PFX "Out of memory\n");
                    goto error;
        }
Signed-off-by: NAdrian Bunk <bunk@stusta.de>
Signed-off-by: NWim Van Sebroeck <wim@iguana.be>
Signed-off-by: NAndrew Morton <akpm@osdl.org>

drivers/char/watchdog/pcwd_usb.c

@@ -705,7 +705,8 @@ static int usb_pcwd_probe(struct usb_interface *interface, const struct usb_devi
 err_out_unregister_reboot:
 	unregister_reboot_notifier(&usb_pcwd_notifier);
 error:
-	usb_pcwd_delete (usb_pcwd);
+	if (usb_pcwd)
+		usb_pcwd_delete(usb_pcwd);
 	usb_pcwd_device = NULL;
 	return retval;
 }